Laurie Spiegel plays 1977 Bell Labs Hal Alles Synth

Concerto for Self-Accompanying Digital Synthesizer. The instrument is possibly the first realtime digital synthesizer, built at Bell Telephone Labs, NJ by Hal Alles and team, with C language software written by Laurie Spiegel that processes the player's live input into an ongoing accompaniment that will continue to be played live against.