The number of different timbres (instruments) a synthesizer can play at a time. Some synthesizers are polyphonic but only monotimbral - ie they can play several sounds but only in the same instrument....
Satellite
This is Moog's response to ARP's Pro-Soloist. It was a preset monophonic synthesizer
with one VCO. Many where built into Organs (see Cordovox) by the Thomas Organ
Company, who also agreed to manufacture and sell 5000 stand-alone units for Moog (at
a royalty of $75 apiece). It featured one thin-sounding VCO and VCF. Presets included
brass, reeds, strings, bell, and lunar.