Are you running OS X?
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ad-hell-aide
If you are, can you do me a favor and right click on the Arduino app, go to Show Package Contents and navigate to the following file, and opening it in a text editor:
Arduino > Contents > Resources > Java > Hardware > Teensy > cores > usb_midi > usb_api.cpp
Do a search for the following line: type2 = b1 & 0xF0; and tell me what the next line of code is.
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Bristol
yup OSX:
it reads:
type2 = b1 & 0xF0;
c = (b1 & 0x0F) + 1;
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ad-hell-aide
Ah yeah, can you do me a favor and remove the + 1? And then re-upload the code?
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Bristol
boom problem solved! strange to be doing that to the channels in the api...
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ad-hell-aide
It's just how I roll. I run a slightly modified version of Teensyduino, and having the channels indexed at 0 instead of at 1 makes more sense (to me).
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Bristol
unnf those square waves.. thank you sir.. having much fun with this little thing!
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ad-hell-aide
Firmware now supports up to four SN76489 chips.
Also added sample support.
http://little-scale.blogspot.com.au/201 … -quad.html
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FRANCE
grea work!
sample support + an armada of pulse waves... now I will make some good use of my 10 SN76489N 
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ad-hell-aide
Maybe not YM2149F because I have none of those here.
But I have about 15 AY38912 chips, so I can make the same thing but for 5 x AY3812 / 38910
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Davie, Florida
Sweet. It'll work for both so it's cool.
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FRANCE
Worth mentioning that as we lower the master clock , we gain access to lower notes but we also reduce the pitch resolution on higher octaves
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Philadelph-ohsh**takecover!!!
If you wanted to get crazy, I'm sure there's a way to switch between clocks based on pitch so you can get the low notes when you need them on the lower clock, and toggle to a faster clock for higher pitches.