- period slides were off by a factor of 4
- we need to reset a note's envelope if it was released, and then
portamento'd into
- instruments shouldn't trigger notes in the presence of 3xx/5xx
fixed many, many bugs, implemented playing (should be relatively
efficient), volume envelopes (but not panning envelopes). found that
instruments start at 1, not 0, and note C-0 is 1, not 0... so it is now
in tune with FT2!
no effects are supported at all yet, and there's a bug where it stops
playing entirely for a while, but "my dirty old kamel" sounds
recognizable and in tune!
