Maybe my search terms are too vague then, but all I have found are archived spec sheets of things like the extinct Holtek or Digital Signal Processors. A DSP would do the job, but I have no idea how I would go about programming two octaves of say 20 voices with a micro and a DSP.
However unless I have missed something, these are all synthesizers, where you are basically setting the resulting instrument up to play your desired note.
The Holtek 3421 was I guess more strictly and organ, it had voices ie piano, violin, organ harpischord etc defined in it, you choose the voice you want to use then bang out your tune on the 2 octave keyboard and it takes care of the whole ADSR etc for you. This is the kind of IC I am trying to find.