Here is a great example of using the uMP3 with a Parallax Basic Stamp. Make sure you set up the bit rate to 2400 bps ("ST D 5"), and the response delay to 5 milliseconds ("ST R 5"). Select either the BS1 (Basic Stamp 1) or BS2 (Basic Stamp 2) version.

Nuts & Volts Volume 6, Column 128 - The Sounds of the Season - by Jon Williams of Parallax