[ENHANCEMENT] Cross-fade power on and hum

[jramboz]

Is it possible to overlap the end of the power on sound with the beginning of the hum sound? Some sound fonts have the hum included as part of the power-on, but not all. For the ones that don't, it's very noticeable that the hum starts after the power-on. Presumably the reverse should be true for power off, but I find that much less noticeable.

It's not a big deal, obviously, but it's a little thing that just sounds... not right. :)