A prototype of a polyphonic analog synth, built by Moog Music in 1983, which never went into production. The SL-8 was intended to be a less expensive synth than the Memorymoog, to compete against the Juno-60 and Prophet-600, but also fix the reliability and tuning stability problems that the Memorymoog suffered from.
The SL-8 nomenclature came from the fact that it would have had 8 voices and bitimbral capability, with each timbre controlled from half of a split keyboard. The voice architecture consisted of one DCO, with a second slave oscillator that could be sync'ed to the DCO in various ways to produce complex timbres. A classic Moog transistor ladder VCF and a Curtis VCA completed the basic voice signal path, and the synth had a built-in chorus effect with programmable rate and depth. The synth had patch memory with 100 locations, and built-in sequencer and arpeggiator capability. All of this was controlled by, and the DCO timing came from, a Texas Instruments TMS 99/4 16-bit microprocessor, which would have made the SL-8 one of the first synths to use 16-bit processing. This also allowed for greater precision in patch parameter digitizing, compared to the competing synths from Roland, Sequential Circuits, and Korg.
One prototype was built, and exhibited at the 1983 NAMM show (with the microprocessor replaced with a TMS 9900 in-circuit emulator and development system, discreetly concealed behind a partition). At the same show, Yamaha introduced the DX7. The Moog personnel listened to demonstrations of the DX7 and concluded that the SL-8 could not compete on either features or price. Moog made a decision to not put the SL-8 into production and to terminate further synth development; this marked the beginning of the end for the original Moog Music. The circuit guts and operating system source code disappeared at some point before Moog's liquidation, and no recordings of the SL-8 are known to survive. The case and panel were saved by an employee, who has since donated them to the Audities Foundation.