I installed a Amsynth from Lucid in Karmic using:
dpkg --force-depends-version -i amsynth_1.2.2-1_i386.deb
The reason for installing the Lucid version is because Karmic version is 3 years old and crashes on my machine. The Lucid Amsynth package depends on newer versions of libatk1 and libjack0 than Karmic has, but I thought I would take a risk, and turns out Amsynth runs fine.
However aptitude tries to uninstall Amsynth every time I do an upgrade. I think I've managed to put it on hold but now aptitude aborts. How can I tell aptitude to ignore the broken package and carry on.