According to a reply on twitter from ohtravioso the long awaiting integration with DopplerPad (and InstantDrummer too I assume) is coming on the 5th of October, so not long to wait now.
FourTrack at the app store:
var addthis_pub = ‘PalmSounds’;http://s7.addthis.com/js/widget.php?v=10
Integration with io.Library would be great too. I guess I'll never use it with FourTrack…
They have talked about ioLibrary integration too.