RY20 uses AWM engine - seemingly related to TG100 GM synth module. It seems to use 12-bit PCM, if YAMAHA kept their usual terminology - they use AWM for 12-bit, and AWM2 for 16-bit PCM. Unlike it's big brother RY30, it's not deeply editable.
2 waveforms layered without a filter.
Pitch, Decay, Pan, Velocity modulations (to level, pitch, waveform balance, etc.) can be modified by relative change..
One reverb/delay effect.
Besides usual drum kits, there is a melody part.
12 Velocity Sensitive Pads
300 Brilliant Voices and 10 Versatile Effects
300 voices from Yamaha's proven AWM (Advanced Wave Memory) tone generator system. A built-in DSP (Digital Signal Processor). Apply one of the six reverbs (hall x 2, room x 2, or plate x 2) or four delays to your drum kits.
A Total of 900 Patterns are Available
50 professionally-programmed preset patterns. 50 user pattern locations and an extra 50 combination pattern locations. Each pattern has six sections (Intro, Main A, Main B, Fill BA, and Ending), and each section contains four tracks (bass drum, snare drum, hi-hat, and other instruments). A total of 900 valuable patterns.
20 User Drum Kits to Modify to Your Own Specifications
Assign any one of the 300 AWM voices to any pad in the drum kit. You can build up your kit, pad bank by pad bank, or just directly access each of the pads.
Change the Groove and Add Some Swing
Add accents and minute timing shifts of a human drummer.
An Efficient Interface and Complete MIDI Implementation