Acronym for the "Programmable Algorithmic Music Synthesizer", a prototype digital synth developed by Yamaha in the 1980-82 time frame. The PAMS used the carrier/modulation operator concept that Yamaha had applied to the GS1 and expanded it, allowing for "algorithms" (different ways in which the operators could be combined in carrier and modulator chains, as opposed to the fixed algorithm employed by the GS1), and multiple types of modulation. It supported phase, amplitude, and true frequency modulation, as well as having some additive synthesis and resynthesis capabilities.
The PAMS itself did not go into production; Yamaha engineers knew that it was too complex to produce a practical model using the technology of the day. It was used for a variety of experiments, including studies to determine which features the DX7 should have. Apparently only one PAMS was built, and its whereabouts today, or whether or not it still exists, are unknown.