Spiegel's best known and most widely used software, "Music Mouse - An Intelligent Instrument" (1986) is for Macintosh, Amiga and Atari computers. The "intelligent instrument" name refers to the program's built-in knowledge of chord and scale convention and stylistic constraints. Automating these processes allows the user to focus on other aspects of the music in real time. In addition to improvisations using this software, Spiegel composed several works for "Music Mouse", including Cavis muris in 1986, Three Sonic Spaces in 1989, and Sound Zones in 1990. She continued to update the program through Macintosh OS 9 and, as of 2012, it remained available for purchase or demo download from her website.