Hello, I just spent about 20 minutes or so moving an iam_eval("stop") statement around in replace_effect, and found out that the call to remove_effect is what causes the crash, though there must be a specific reason for it, since remove_effect doesn't otherwise cause ecasound to crash. For now, I stop the engine before remove_effect and restart it at the end of the subroutine, which gives me bypass with a hickup, but no crash. BTW, mute/solo seem to be behaving stably so far. Cheers, S.M. --