Archive for category fun
The new Spotify Web API allows the developer to create and add tracks to a playlist on behalf of a listener. This is a pretty powerful feature, opening the door for a whole range of apps. For instance, this weekend, I added the ability to save a Roadtrip Mixtape playlist, so you can now actually take your mixtapes on the road. The code is on github if you are interested in seeing how it is done.
Last week at the SXSW Music Hack Championship hackathon I built The Autocanonizer. An app that tries to turn any song into a canon by playing it against a copy of itself. In this post, I explain how it works.
At the core of The Autocanonizer are three functions – (1) Build simultaneous audio streams for the two voices of the canon (2) Play them back simultaneously, (3) Supply a visualization that gives the listener an idea of what is happening under the hood. Let’s look at each of these 3 functions:
(1A) Build simultaneous audio streams – finding similar sounding beats
The goal of the Autocanonizer is to fold a song in on itself in such a way that the result still sounds musical. To do this, we use The Echo Nest analyzer and the jremix library to do much of the heavy lifting. First we use the analyzer to break the song down into beats. Each beat is associated with a timestamp, a duration, a confidence and a set of overlapping audio segments. An audio segment contains a detailed description of a single audio event in the song. It includes harmonic data (i.e. the pitch content), timbral data (the texture of the sound) and a loudness profile. Using this info we can create a Beat Distance Function (BDF) that will return a value that represents the relative distance between any two beats in the audio space. Beats that are close together in this space sound very similar, beats that are far apart sound very different. The BDF works by calculating the average distance between overlapping segments of the two beats where the distance between any two segments is a weighted combination of the euclidean distance between the pitch, timbral, loudness, duration and confidence vectors. The weights control which part of the sound takes more precedence in determining beat distance. For instance we can give more weight to the harmonic content of a beat, or the timbral quality of the beat. There’s no hard science for selecting the weights, I just picked some weights to start with and tweaked them a few times based on how well it worked. I started with the same weights that I used when creating the Infinite Jukebox (which also relies on beat similarity), but ultimately gave more weight to the harmonic component since good harmony is so important to The Autocanonizer.
(1B) Build simultaneous audio streams – building the canon
The next challenge, and perhaps biggest challenge of the whole app, is to build the canon – that is – given the Beat Distance Function, create two audio streams, one beat at a time, that sound good when played simultaneously. The first stream is easy, we’ll just play the beats in normal beat order. It’s the second stream, the canon stream that we have to worry about. The challenge: put the beats in the canon stream in an order such that (1) the beats are in a different order than the main stream, and (2) they sound good when played with the main stream.
The first thing we can try is to make each beat in the canon stream be the most similar sounding beat to the corresponding beat in the main stream. If we do that we end up with something that looks like this:
It’s a rat’s nest of connections, very little structure is evident. You can listen to what it sounds like by clicking here: Experimental Rat’s Nest version of Someone Like You (autocanonized). It’s worth a listen to get a sense of where we start from. So why does this bounce all over the place like this? There are lots of reasons: First, there’s lots of repetition in music – so if I’m in the first chorus, the most similar beat may be in the second or third chorus – both may sound very similar and it is practically a roll of the dice which one will win leading to much bouncing between the two choruses. Second – since we have to find a similar beat for every beat, even beats that have no near neighbors have to be forced into the graph which turns it into spaghetti. Finally, the underlying beat distance function relies on weights that are hard to generalize for all songs leading to more noise. The bottom line is that this simple approach leads to a chaotic and mostly non-musical canon with head-jarring transitions on the canon channel. We need to do better.
There are glimmers of musicality in this version though. Every once in a while, the canon channel will remaining on a single sequential set of beats for a little while. When this happens, it sounds much more musical. If we can make this happen more often, then we may end up with a better sounding canon. The challenge then is to find a way to identify long consecutive strands of beats that fit well with the main stream. One approach is to break down the main stream into a set of musically coherent phrases and align each of those phrases with a similar sounding coherent phrase. This will help us avoid the many head-jarring transitions that occur in the previous rat’s nest example. But how do we break a song down into coherent phrases? Luckily, it is already done for us. The Echo Nest analysis includes a breakdown of a song into sections – high level musically coherent phrases in the song – exactly what we are looking for. We can use the sections to drive the mapping. Note that breaking a song down into sections is still an open research problem – there’s no perfect algorithm for it yet, but The Echo Nest algorithm is a state-of-the-art algorithm that is probably as good as it gets. Luckily, for this task, we don’t need a perfect algorithm. In the above visualization you can see the sections. Here’s a blown up version – each of the horizontal colored rectangles represents one section:
You can see that this song has 11 sections. Our goal then is to get a sequence of beats for the canon stream that aligns well with the beats of each section. To make things at little easier to see, lets focus in on a single section. The following visualization shows the similar beat graph for a single section (section 3) in the song:
You can see bundles of edges leaving section 3 bound for section 5 and 6. We could use these bundles to find most similar sections and simply overlap these sections. However, given that sections are rarely the same length nor are they likely to be aligned to similar sounding musical events, it is unlikely that this would give a good listening experience. However, we can still use this bundling to our advantage. Remember, our goal is to find a good coherent sequence of beats for the canon stream. We can make a simplifying rule that we will select a single sequence of beats for the canon stream to align with each section. The challenge, then, is to simply pick the best sequence for each section. We can use these edge bundles to help us do this. For each beat in the main stream section we calculate the distance to its most similar sounding beat. We aggregate these counts and find the most commonly occurring distance. For example, there are 64 beats in Section 3. The most common occurring jump distance to a sibling beat is 184 beats away. There are ten beats in the section with a similar beat at this distance. We then use this most common distance of 184 to generate the canon stream for the entire section. For each beat of this section in the main stream, we add a beat in the canon stream that is 184 beats away from the main stream beat. Thus for each main stream section we find the most similar matching stream of beats for the canon stream. This visualizing shows the corresponding canon beat for each beat in the main stream.
This has a number of good properties. First, the segments don’t need to be perfectly aligned with each other. Note, in the above visualization that the similar beats to section 3 span across section 5 and 6. If there are two separate chorus segments that should overlap, it is no problem if they don’t start at the exactly the same point in the chorus. The inter-beat distance will sort it all out. Second, we get good behavior even for sections that have no strong complimentary section. For instance, the second section is mostly self-similar, so this approach aligns the section with a copy of itself offset by a few beats leading to a very nice call and answer.
That’s the core mechanism of the autocanonizer – for each section in the song, find the most commonly occurring distance to a sibling beat, and then generate the canon stream by assembling beats using that most commonly occurring distance. The algorithm is not perfect. It fails badly on some songs, but for many songs it generates a really good cannon affect. The gallery has 20 or so of my favorites.
(2) Play the streams back simultaneously
When I first released my hack, to actually render the two streams as audio, I played each beat of the two streams simultaneously using the web audio API. This was the easiest thing to do, but for many songs this results in some very noticeable audio artifacts at the beat boundaries. Any time there’s an interruption in the audio stream there’s likely to be a click or a pop. For this to be a viable hack that I want to show people I really needed to get rid of those artifacts. To do this I take advantage of the fact that for the most part we are playing longer sequences of continuous beats. So instead of playing a single beat at a time, I queue up the remaining beats in the song, as a single queued buffer. When it is time to play the next beat, I check to see if is the same that would naturally play if I let the currently playing queue continue. If it is I ‘let it ride’ so to speak. The next beat plays seamlessly without any audio artifacts. I can do this for both the main stream and the canon stream. This virtually elimianates all the pops and clicks. However, there’s a complicating factor. A song can vary in tempo throughout, so the canon stream and the main stream can easily get out of sync. To remedy this, at every beat we calculate the accumulated timing error between the two streams. If this error exceeds a certain threshold (currently 50ms), the canon stream is resync’d starting from the current beat. Thus, we can keep both streams in sync with each other while minimizing the need to explicitly queue beats that results in the audio artifacts. The result is an audio stream that is nearly click free.
(3) Supply a visualization that gives the listener an idea of how the app works
I’ve found with many of these remixing apps, giving the listener a visualization that helps them understand what is happening under the hood is a key part of the hack. The first visualization that accompanied my hack was rather lame:
It showed the beats lined up in a row, colored by the timbral data. The two playback streams were represented by two ‘tape heads’ – the red tape head playing the main stream and the green head showing the canon stream. You could click on beats to play different parts of the song, but it didn’t really give you an idea what was going on under the hood. In the few days since the hackathon, I’ve spent a few hours upgrading the visualization to be something better. I did four things: Reveal more about the song structure, show the song sections, show, the canon graph and animate the transitions.
Reveal more about the song
The colored bars don’t really tell you too much about the song. With a good song visualization you should be able to tell the difference between two songs that you know just by looking at the visualization. In addition to the timbral coloring, showing the loudness at each beat should reveal some of the song structure. Here’s a plot that shows the beat-by-beat loudness for the song stairway to heaven.
You can see the steady build in volume over the course of the song. But it is still less than an ideal plot. First of all, one would expect the build for a song like Stairway to Heaven to be more dramatic than this slight incline shows. This is because the loudness scale is a logarithmic scale. We can get back some of the dynamic range by converting to a linear scale like so:
This is much better, but the noise still dominates the plot. We can smooth out the noise by taking a windowed average of the loudness for each beat. Unfortunately, that also softens the sharp edges so that short events, like ‘the drop’ could get lost. We want to be able to preserve the edges for significant edges while still eliminating much of the noise. A good way to do this is to use a median filter instead of a mean filter. When we apply such a filter we get a plot that looks like this:
The noise is gone, but we still have all the nice sharp edges. Now there’s enough info to help us distinguish between two well known songs. See if you can tell which of the following songs is ‘A day in the life’ by The Beatles and which one is ‘Hey Jude’ by The Beatles.
Show the song sections
As part of the visualization upgrades I wanted to show the song sections to help show where the canon phrase boundaries are. To do this I created a the simple set of colored blocks along the baseline. Each one aligns with a section. The colors are assigned randomly.
Show the canon graph and animate the transitions.
To help the listener understand how the canon is structured, I show the canon transitions as arcs along the bottom of the graph. When the song is playing, the green cursor, representing the canon stream animates along the graph giving the listener a dynamic view of what is going on. The animations were fun to do. They weren’t built into Raphael, instead I got to do them manually. I’m pretty pleased with how they came out.
All in all I think the visualization is pretty neat now compared to where it was after the hack. It is colorful and eye catching. It tells you quite a bit about the structure and make up of a song (including detailed loudness, timbral and section info). It shows how the song will be represented as a canon, and when the song is playing it animates to show you exactly what parts of the song are being played against each other. You can interact with the vizualization by clicking on it to listen to any particular part of the canon.
Wrapping up – this was a fun hack and the results are pretty unique. I don’t know of any other auto-canonizing apps out there. It was pretty fun to demo that hack at the SXSW Music Hack Championships too. People really seemed to like it and even applauded spontaneously in the middle of my demo. The updates I’ve made since then – such as fixing the audio glitches and giving the visualization a face lift make it ready for the world to come and visit. Now I just need to wait for them to come.
In my recent regional listening preferences post I published a map that showed the distinctive artists by state. The map was rather popular, but unfortunately was a source of confusion for some who thought that the map was showing the favorite artist by state. A few folks have asked what the map of favorite artists per state would look like and how it would compare to the distinctive map. Here are the two maps for comparison.
Favorite Artists by State
This map shows the most played artist in each state over the last year. It is interesting to see the regional differences in favorite artists and how just a handful of artists dominates the listening of wide areas of the country.
Most Distinctive Artists by State
This is the previously published map that shows the artists that are listened to proportionally more frequently in a particular state than they are in all of the United States.
The data for both maps is drawn from an aggregation of data across a wide range of music services powered by The Echo Nest and is based on the listening behavior of a quarter million online music listeners.
It is interesting to see that even when we consider just the most popular artists, we can see regionalisms in listening preferences. I’ve highlighted the regions with color on this version of the map:
Favorite Artist Regions
This past weekend was the fourth annual MIDEM Music Hack Day held in Cannes. During about 48 hours 2 dozen or so hackers collected in a beautiful hacking space at the top of the Palais Des Festivals to build something cool with music and technology.
The MIDEM Music Hack Day is no ordinary Music Hack Day. It has a very limited enrollment so only hackers that have demonstrated the ability to create music hacks are invited. Add to that, the fact that there is about 50% more time to build hacks and the result is a set of very high quality hacks.
Martyn Davies, master Music Hack day coordinator, kicked off the event with a talk to the MIDEM attendees about what Music Hack Day is all about. Martyn talked about the things that drive the hackers to spend their weekends hacking on code – in particular how the Music Hack Day is a chance to combined their love for music and technology, be creative and to build something new and cool during the weekend. Martyn demonstrated two representative hacks built at previous Music Hack Days. First he showed the demo given by master hacker @sydlawrence of a hack called Disco Disco Tech. The excitement in Syd’s voice is worth the price of admission alone.
Next he showed one of my favorite Music Hack Day hacks of all time, Johnny Cash is Everywhere by @iainmullen
One of the special features of the MIDEM Music Hack Day is that non-hackers get to pitch their hacking ideas to the hackers about what apps they’d really like to see created over the weekend. There were a number of pitches ranging from a proposal for an artist-centric tool for organizing a creative music production team to a whimsical request to show what the music on the Internet sounds like when it decays. (Here’s one answer). All of the idea pitches were interesting, but here’s the secret. The hackers are not going to build your idea. It’s not because they don’t like your idea, it is because they already have tons of good ideas. The hackers are a very creative bunch, each with a long list of ideas waiting to be built. What the hackers usually lack is a solid block of time to implement their own ideas and so a hackathon is the perfect time to take that best idea on the list and work for a solid 24 hour to get it done. It is rare for a hacker to get excited about building someone else’s idea, when they have so many of their own. As they say: “ideas are cheap, execution is everything“.
Once the opening talks concluded we hackers made their way up to the top of the Palais des Festivals (the heart of MIDEM) to our hacking space. It’s a great space with lots of natural light, a terrace that overlooks the French Riviera, and it is some distance away from the main conference so we were not bothered by stray walk-ons.
To kick things off, we went around the room introducing ourselves, briefly talking about our background skills, and ideas, and almost immediately got to hacking. Since all the hackers were experienced hackers there was no need for the typical API workshops or learning sessions. Everyone knew, for instance, that I was from The Echo Nest and was ready to answer any questions about the Echo Nest API that should arise.
The next 46 hours was a blur of coding, punctuated by food delivery, the sound of the espresso maker and the occasional wandering pigeon.
Hacker Self Portraits
There’s a math error lurking in there …
Early morning coding on the French Riveria
After 48 hours, we gathered in the Innovation Hall to demonstrate what we built. Each hacking team had about three minutes to show their stuff. Eighteen hacks were built. Here are some of my very favorites:
DJ Spotify – built by Yuli Levtov – This is a real hacker’s hack. Yuli had a problem. He wanted to use Spotify when he DJed, but Spotify won’t let you beat match and cross fade songs. In fact, Spotify won’t even let you play two streams at once. So Yuli got to work to make it happen. Along the way Yuli augmented his DJ playlists with BPM and key information from The Echo Nest (using a very clever growl hack). One of the highlights of my MIDEM week was listening to Yuli try to explain what OS virtualization is and how Soundflower works to a room full of Music Biz types. Yuli has a detailed blog post that describes how his hack works. Yuli’s hack was voted the best hack by the hackers. Well done Yuli!
That One Song – by Matt Ogle and Hannah Donovan – For this hack, Matt added a feature to his super popular This Is My Jam site. Type in any band and let the Jam community tell you the one song you should hear first. Plus: playback options, commentary, and an alternative “B-side” song recommendation for each artist.
Skrillex Invader 20 – by Vivien Barousse – Imagine Guitar Hero meets Space Invaders meets Skrillex meets a Piano Keyboard. Skrillex Invader 20 is a small game designed to help you improve your skills on a piano keyboard.
Scratchy Record – by Alastair Porter – Playing music from mp3s today has no soul. Scratchy Record reproduces the joy that can be had listening to music on vinyl. From the dirty needle causing extra noise, to the pops and skips that we all love, to the need to get up half way through the album and turn it over. Scratchy Record has it all.
HappyClappy – by Peck, ankit and mager – an IOS app that lets you queue up songs by clapping the rhythm. Uses The Echo Nest to search for songs by BPM.
PhatStats – Syd Lawerence – Syd tried to build a sustainable subscription business during the hack with PhatStats – A new tool to discover up and coming talent across the social web, and to monitor your videos and their engagement levels across the social web.
This is your tour – Sam Phippen – Going on tour is hard. You’ve got to find someone to tour with. You’ve got to pick cities and venues. You’ve got to book hotels, find places to eat and drink. All of this takes far too much time.
Nikantas – Sabrina Leandro – a clever app that helps you learn a new language through music lyrics. Fill in the blanks in lyrics of your favourite English, Spanish, Portuguese, French, German, or Italian artists. Can you recognise a word in a song? A word will be displayed on the screen, press the space key when the artist sings it
neoScores meets Deezer – Bob Hamblok – HTML5 sheet music score following inside Deezer.
Seevl hipster – by Alexandre Passant – Be a real hipster. Impress your friends with obscure music tastes. Do you want to impress your friend who’s into electro-folk, or that other one who only listens to avant-garde metal? Now you can! With seevl hipster, find obscure artists that match your friend tastes, and show-off on their Facebook wall.
Playlist Plus – Iain Mullan – Playlist Plus allows you to create a richer interactive version of a playlist. Add notes and comments to each track, to share with friends, or distribute an in-depth album review. Like a particular lyric? Bookmark it at the exact timestamp in the song. Think a track has a heavy Zeppelin influence? Link to the song/album it reminds you of. Cover version? Link to the original and let the reader stream it instantly from within your PlaylistPlus!
ScapeList – Mohammed Sordo – How does a landscape sound like? You take a picture of, let’s say, the Grand Canyon in Colorado, a la Instagram, but you also want to attach a song to it, a song that makes sense to you while you were taking that picture. Now imagine that other people went to the same place, took another picture of it but picked a different song. You end up with a playlist of songs related to that landscape, a ScapeList, curated by the users themselves, which you can listen to.
VideoFairy – by Suzie Blackman – A radio-style music discovery app designed for smart TV! It’s a bit like channel hopping, but for music videos. VideoFairy finds music videos from artists you’ll like with a simple interface that works with a remote control (use arrow keys and ‘enter’ on a keyboard).Designed for ‘lean back’ TV viewing with minimum interaction, you can sit back and watch new music recommended from your last.fm profile. Skip skip anything you don’t like with a simple tap of the remote.
Cannes Burn – my hack – a music visualizaton of Ellie Goulding’s Burn
I was unusually nervous and quite tired when I gave my demo, so I fell for a newbie demo mistake and had trouble getting my desktop to display properly. But when I finally did, my demo went off smoothly. I only had to say a few words and hit the play button, so despite the nerves, it was a pretty easy demo to give. Here’s my view of the audience while giving the demo:
After we presented the hacks the hackers themselves voted for the best hack which went to Yuli for his amazing DJ Spotify. Yuli is quite the gracious and humble winner, making sure everyone got a glass of his winning champagne.
After all the hacking the exhausted hackers took some time to kick back, have a good dinner, a few drinks and long conversations into the night about life as an international music hacker.
Halfway through the MIDEM Music Hack Day I paused to take stock. Here I was, on the other side of the world sitting at the top of the Palais des Festival, overlooking the French Riviera, surrounded by friends and writing code. It was a great place to be, and I felt very fortunate to be there. This was all possible because the music biz folks realize that we hackers have lots of ideas that will advance the state-of-the-art in music tech, and even more importantly we have the ability to actually turn those ideas into reality. And so, they treat us very well. It is good to be a music hacker.
My hack at the MIDEM Music Hack Day this year is what I’d call a Creative Hack. I built it, not because it answered any business use case or because it demonstrated some advanced capability of some platform or music tech ecosystem, I built it because I was feeling creative and I wanted to express my creativity in the best way that I can which is to write a computer program. The result is something I’m particularly proud of. It’s a dynamic visualization of the song Burn by Ellie Goulding. Here’s a short, low-res excerpt, but I strongly suggest that you go and watch the full version here: Cannes Burn[youtube http://www.youtube.com/watch?v=Fys0RGi3kA8&feature=youtu.be]
Unlike all of the other hacks that I’ve built, this one feels really personal to me. I wasn’t just trying to solve a technical problem. I was trying to capture the essence of the song in code, trying to tell its story and maybe even touch the viewer. The challenge wasn’t in the coding it was in the feeling.
After every hack day, I’m usually feeling a little depressed. I call it post-hacking depression. It is partially caused by being sleep deprived for 48 hours, but the biggest component is that I’ve put my all into something for 48 hours and then it is just over. The demo is done, the code is checked into github, the app is deployed online and people are visiting it (or not). The thing that just totally and completely took over my life for two days is completely gone. It is easy to reflect back on the weekend and wonder if all that time and energy was worth it.
Monday night after the MIDEM hack day was over I was in the midst of my post-hack depression sitting in a little pub called Le Crillon when a guy came up to me and said “I saw your hack. It made me feel something. Your hack moved me.”
Cannes Burn won’t be my post popular hack, nor is it my most challenging hack, but it may be my favorite hack because I was able to write some code and make somebody that I didn’t know feel something.
For my Christmas vacation programming project this year, I revisited an old hack: Six Degrees of Black Sabbath. I wrote the original, way back in 2010 at the very first San Francisco Music Hack Day. That version is still up and running, and getting regular visits, but it is getting a bit long in the tooth and so I’ve given it a total rewrite from the ground up. The result is the new Six Degrees of Black Sabbath:
Six Degrees of Black Sabbath is like the Oracle of Bacon but for music. It lets you find connections to just about any two artists based upon their collaborations. Type in the name of two artists, and 6dobs will give you a pathway showing the connections that will get you from one artist to another. For instance, if you enter ‘The Beatles’ and ‘Norah Jones’ you’ll get a path like:
- We start with The Beatles
- The Beatles had member George Harrison
- George Harrison performed with Ravi Shankar on the song Bangla Dhun and 26 others.
- Ravi Shankar was parent of Norah Jones
If you don’t like a particular connection, you can bypass it generating a new path. For instance, if we bypass Ravi Shankar, it will take us eight steps to get to Norah Jones from the Beatles:
The Beatles -> Paul McCartney -> The Fireman -> Youth -> Pigface
-> Mike Dillon ->Garage A Trois -> Charlie Hunter -> Norah Jones
Not all connections are created equal. Mick Jagger and Keith Richards have been playing together for over 50 years in the Rolling Stones. That’s a much stronger connection than the one between Mick Jagger and Fergie for performing a single song together at the Rock and Roll Hall of Fame. We take these connection strengths into account when finding paths between artists. Preference is given to stronger connections, even if those stronger connections will yield a longer path.
The new version of Six Degrees of Black Sabbath has a number of new features:
Video – Each step in a path is represented by a Youtube video – often with a video by the two artists that represent that step. I’m quite pleased at how well the video works for establishing the connection between two artists. Youtube seems to have it all.
Live stats – The app tracks and reports all sorts of things such as the longest path discovered so far, the most frequently occurring artists on paths, the most connected artists, most searched for artists and so on.
Larger database of connections – the database has about a quarter million artists and 2.5 million artist-to-artist connections.
Autocomplete for artist names – no need to try to remember how to spell ‘Britney Spears‘ – just start typing the parts you know and it will sort it out.
Spiffier looking UI – It still looks like it was designed by an engineer, but at least it looks like it was designed in this decade by an engineer.
Path finding improvements – faster and better paths throughout.
Revisiting this app after 4 years was a lot of fun. I got to dive deep into a bunch of tech that was new to me including Redis, Bootstrap 3, and the YouTube video search API. I spent many hours untangling the various connections in the new Musicbrainz schema. I took a tour through a number of Pythonic network graph libraries (Networkx, igraph and graph-tool), I learned a lot about Python garbage collection when you have a 2.5gb heap.
Give the app a try and let me know what you think.
This weekend, I’ve been in London, attending the London Music Hack Day. For this weekend’s hack, I was inspired by daughter’s music listening behavior – when she listens to music, she is good for the first verse or two and the chorus, but after that, she’s on to the next song. She probably has never heard a bridge. So for my daughter, and folks like her with short attention spans, I’ve built Attention Deficit Radio. ADR creates a Pandora-like radio station based upon a seed artist, but doesn’t bother you by playing whole songs. Instead, after about 30 seconds or so, it is on to the next song. The nifty bit is that ADR will try to beat-match and crossfade between the songs giving you a (hopefully) seamless listening experience as you fly through the playlist. Of course those with short attention spans need something to look at while listening, so ADR has lots of gauges that show the radio status – it shows the current beat, the status of the cross-fade, tempo and song loading status.
There may be a few rough edges, and the paint is not yet dry, but give Attention Deficit Radio a try if you have a short listening attention span.