I’ve been in Helsinki this weekend (which is not in Sweden btw) for the Helsinki Music Hack Day.  I wanted to try my hand at a DJ app that will allow you to dynamically and interactively mix two songs.  I started with Girl Talk in a Box, ripped out the innards and made a whole bunch of neat changes:

1. You can load more than one song at a time. Each song will appear as its own block of music tiles.
2. You can seamlessly play tiles from either song.
3. You can setup branch points to let you jump from an point in one song to any point in another (or the same) song.
   
4. And the killer feature – you can have two active play heads  allowing you to dynamically interact with two separate audio streams.  The two play heads are always beat matched (the first play head is the master that sets the tempo for everyone else). You can cross-fade between the two audio streams – letting you move different parts of the song into the foreground and the background.

All the regular features of Girl Talk in a Box are retained – bookmarks, arrow key control, w/a/s/d navigation and so on.  See the help for more details on the controls.

You can try the app here:  Swap the Drop