Formant Sequencing
The FS1R uses the "formant sequence", this being a series (128 or 512) of "frames" that define the level and frequency of each of up to 8 'voiced' (pitched) and 8 'unvoiced' (un-pitched) formant generators over time. The number of frames limits the typical length of a sequence to a few seconds, though this length and pitch can be varied in real-time with few or no artefacts. Applying a formant sequence to a sound allows a complex, evolving sound to be programmed in a relatively short time. 90 formant sequences were supplied with the FS1R.
Read more about this topic: Yamaha FS1R