Practical Solutions debuted Tweety Board at an Atari Fest in Glendale, California. Tweety Board is a solderless upgrade that enables any ST to produce stereo sound. A hardware adaptor with three RCA phono jacks connects to the RS-232 port on the ST; you can add two speakers for conventional stereo sound or three for full surround-sound capability. The adaptor also includes a pass-through that lets you connect other RS-232 devices to your ST. Tweety Board is expected to cost $49.95. 

It is capable of generating true stereo output if you have a three channel input receiver.  For those of us with only amps and speakers, two channels are combined into one channel on the amp.  The results is the vibrant sound that we all know that the ST is capable of.

The actual Tweety Board consists of a small board with a pin adaptor to fitover your Yamaha sound chip, and an external connector with three RCA jacks to your stereo or amp.  Installation is simple and the documentation is very good on this.  Installation should take no more than half an hour if you are good with electronics.  If you are not, then the manual advises you to have a technical person disassemble your ST.