Sometimes sf2 and vsts just hang, as if I haven't let go of a key. If there was a way to forcefully 'kill', that is mute, stop all currently playing sounds I wouldnt at least have to restart LMMS each time. Theres a similar feature in other software, like ZynAddSubFX, it has a button called "Stop all sounds!"...
agree, but on the general vst GUI there is a button "turn off all notes", so the problem is with sf2. I even believe that there was a general 'panic-button' on early version on lmms, but a restart was needed anyway, because Hangnotes has a really peculiar behavior: If a hangnote is re-trickered after a panic-press, it will re-enter the hang -so a force-mute is not enough. Believe it is something outside lmms that causes this problem.
A ticket has been raised in the bug-report area in regard to zynAddSubFX hangnotes, and the team is working on this.
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FYI
Toby has already tackled the zynAddSubFX issue. a preview version of upcoming release of 0.4.10 has this fixed.