Andrew Gaydenko:
The only sound editor I know to _work_ with jack is
https://gna.org/projects/mhwaveedit/
All others declare jack support only.
SND works just fine with jack:
http://ccrma.stanford.edu/software/snd/
For example, can you set up a great sounding midi softsynth
completely running inside the jack realtime thread using only
90 lines with mhwaveedit?
http://tinyurl.com/borbp