This is an Altair controlled hardware synth I take it? Now *MY* Altair Synth (pardon the ego!) was all done in software, with a simple 8-bit d/a converter on an i/o port. It used 256 bytes of a waveform (fundamental sin(x) plus some harmonics) that were stepped thru by up to 4 pointers at various rates and added up to get 4 part harmony. Took a lot of instruction cycle counting to get the timing just right and was worked up to where one could, with a lot of tedious data entry, type in a Bach invention (#8 - was on 'Switched on Bach') and have it play perfectly. Now, being a 2Mhz machine it sang bass and tenor mostly. Spent many a long night getting one together for a school software contest and the prof. gave the prize to a lousy serial auto-baud detector (probably because HE suggested it). So we learned that demo's need BIG speakers to make an impression :)) A# = (12th root of 2) * 440Hz B = " * A# Chuck cswiger(a)widomaker.com