Qsynth playing out of tune, and using SFArk files in Linux
Gave QSynth (a Qt front-end for fluidsynth) a whirl today and couldn't work out why it was playing "out of tune", as if it was transposed up about a step.
It turns out that QSynth defaults to 44100Hz for the Jack output rate, rather than detecting what samplerate jackd is already using. The fix is quite simple - go into the engine settings and set the samplerate to match what you are using in Jack.
Oh - and if you are trying out some soundfonts and need to unpack an SFArk file to an sf file, it turns out that the makers of sfark now have a linux version of the decompressor available, at http://www.melodymachine.com/sfark.htm (yep, it works fine on a 64-bit system too). Failing that, apparently the win32 client works ok in wine as well.