The Moog Tauris I is a monophonic analog bass synthesizer that you play with a foot pedal, so you can play additional bass notes to the instrument in your hand. The Taurus has become famous for its incredibly deep and rich bass sound and not least because bands like Genesis, Yes, Rush, Dream Theater and many more used it in their songs.
Geddy Lee, a band member of Rush, once said in an interview, that their producer loves the sound of the Moog Taurus so much that they would like to give him shoes with Taurus pedals attached so that he can hear Taurus bass sounds with every step he takes.