The Covox Speech thing was a simple resistor ladder DAC that attaches to the PC LPT port, it can playback 8-bit audio samples, of nearly any frequency (just limited by how fast the CPU can send data to the LPT port). Covox originally released the Speech Thing in 1987 for $79, though people quickly realized they could build their own for much less, so REAL Covox devices are quite rare these days, but the clones are very common.
I ordered some PCBs (found random PCB gerbers in a google search) and built up these Covox Speech Thing clones (I used SMD components for some extra SMD solder practice, and smaller device footprint).
Here’s a partial build video, soldering the SMD parts.
Here’s some video of the Speech Thing in action.
Some of the directly supported games
There’s also some TSR’s available to emulate Tandy sound or the Disney Sound Source. however these require at least a 386, and I believe only work with real-mode games.