PartyCloud.fm - is an online, two deck DJ mixing / mashup app which takes it's music source from SoundCloud. This is where they get the 20 million song figure from.Though I couldnt find everything - not sure of the criteria they use, but there was still a heck of a lot of tunes to rifle through.
The twin deck setup launches in your browser as a fairly familiar setup with level, crossfade, beat match, 2 ,4 and 8 beat looping and effects. It's piece of cake to use - even for a numpty (non) DJ like me, though of course, my impeccable taste in music still shines through.
It's kind of like a DJ interface for Soundcloud and it just works, with the beat sync I was able to create passable transitions and cut ups (at least to my ears) in seconds.
Another cool feature is the ability to record your 'set' - though you will need to connect your Facebook account to do this. What is even niftier, is that while you are recording, other people can tune in and watch your performance with the interface following the performers actions - try it, you'll see what I mean.
A right click on the interface brings up a MIDI control option, which I believe is under development - sadly I couldn't get any of my MIDI controllers to speak to it, nor could I find any key commands. In fact information is rather light, but I guess it's pretty self evident on how to use PartyCloud on a basic level. Another useful feature is the mono program and cue output so you can setup a cue mix with a mono Y headphone split.
With MIDI control this thing could really rock the party - though only in mono if you want a cuemix -and assuming you can find the tunes you want to play. Which is the only real downside - you can only mine Soundcloud for tunes. But even with these ingredients missing, you can't fail but to have a bit of fun.
Check it out yourself, but make sure you have a couple of hours spare- its addictive...