Texas Instruments SN76489

The Texas Instruments SN76489, was a soundchip most notably used in by Sega(in the Megadrive, Master System and Game Gear) as well as the BBC Micro.

Like the Gameboy, it is capable of producing 3 squarewaves and a pseudo-random noise output.
In his blog, Sebastian Tomzcak(little scale) has been documenting the control of this chip via Arduino. Documentation and results can be found here and here.
More information on the chip itself can be found here.