Feature/mono mode

[yokemura]

Summary

resolves #8 resolves #9

Implemented Monophonic Mode.

Monophonic Mode includes

• Legato
• Portamento
• Arpeggio

Technical Info

Extended Synthesizer to alter the note-on behavior. In Monophonic Mode, NoteOn is triggered only on the first key-on, and successive key-on just changes the parameter of the sounding note.

[yokemura]

I myself have used this feature for a month or so and have proven it's basically working.

But it still has a serious bug: Sometimes it stops sounding while using arpeggiator. I still haven't figured out how to reproduce it, but it's likely to happen when you have some notes where their note-offs have slight difference in time.

What I've found so far about the issue

• It happens only the notes are played in a sequence (mine is Logic Pro X. I still haven't tested in other DAWs).
• Once the midi in the sequence is forwarded to an external source it doesn't happen. Specifically setting the MIDI output or Logic to IAC Driver and receiving it with standalone build of Magical 8bit Plug.
• It happens with MIDI sequence with a certain condition which is still unknown. If you put the notes directly in the PianoRoll of Logic it works right, but imported SMF file can cause the issue. The only difference I've found between the one I put on pianoroll and the imported one is note-off velocity. The former is set to 64 and the latter is set to 0. But I'm not sure yet if it's the cause of the issue.
• Having said "while using arpeggiator" above, but it happens in Legato mode, too. In the case of Legato mode the note won't stop at all. Seems like the note retirement behavior will break with some specific MIDI sequence.

[yokemura]

The issue above is now fixed.

It was happening when the MIDI channel of note-on and one of note-off are different. My MIDI sequence contained notes of different MIDI channels in a single track (it was because I merged some MIDI tracks without knowing they are designated to each MIDI destination). And it didn't happen while forwarding to IAC driver because IAC driver resends the event with its specified MIDI channel.

[yokemura]

TODO: Keep arpeggiated in release phase With current implementation it forgets the arpeggio notes immediately on a key-off. As result when the last key is released the arpeggio information is no longer available, and nothing sounds in the release phase. To avoid this it should remember the arpeggio notes for a while after the key-off. The problem is how long is "a while". If it's too long the tone will remain after key-off, which is not desirable. My idea is to move the arpeggio note retirement process to the place of arpeggio note alternation. This way the arpeggio info will be retained for 1 control frame at maximum. At least it will work with well-aligned sequence notes.

[yokemura]

Solved. It worked with my above idea.

[yokemura]

I used it for quite a bit of time and nothing seems to go wrong, so merge it.