Here's another oddity - the Digispeech DS201A "Speech & Music Unit."

This little device has a number of things going for it. Using a customized DSP, it's capable of playing-back a number of different (and in some cases, esoteric) digital audio and speech synthesis formats, and is somewhat compatible with IBM's PS/2 Speech Adapter. (This functionality didn't work in two games I tried that supposedly have support for the IBM device.)
Here's an interesting bit of apocrypha to help describe the "music" side of the equation:
"The DS201 and DS201A Audio Adapters contain a three voice tone generator which emulates the Complex Sound Generator (SN76496N) device used in IBM PC-Junior and Tandy computers. The DIGI drivers provide BIOS-level compatibility for programs written for these machines via the INT 4D API."
Awesome, right?! Tandy music on your non-Tandy PC!
Well, not exactly, no.
First of all, the noise channel isn't "emulated," and second... I've not been able to get anything to play 3-voice music through this thing at all.
Did I mention that it plugs into a serial port? 😀