via this auction
"This is the Synth Expansion for the Quasimidi Rave-O-Lution 309 Groovebox / Synthesizer...
SYNTH EXPANSION
Whether you buy one or all three expansion options, your 309's operating system needs to be upgraded to v2.0 (see 'v2.0 Software' box). Luckily, this upgrade is provided as a matter of course, and is easily installed by simply removing a plate from the 309's bottom and swapping the old chip for the new one. Full, clear instructions are given, as is the necessary chip-removal tool.
On either side of the main operating system chip there's a socket where the synth and drum/percussion expansion options are installed. Essentially, the synth expansion adds 37 new oscillator models, offering up to four oscillators each, two new filter algorithms (12dB low-pass and 12dB high-pass), plus sequence-sync'able LFOs. You can now assign 16th, 8th, quarter and whole note values, that follow the 309's tempo, to the LFO. The new waveforms can be auditioned in 32 example sounds, but these memory locations are not accessible under normal circumstances. There are still 128 synth patch memory locations.
The synth expansion offers one -- or is that two? -- especially important new feature if the audio expansion option is also installed: two extra bass/lead synths. These synths can be played on their own MIDI channels, from an external keyboard or sequencer, or set up to double the main bass/lead synth. It's also possible to trigger the extra synths from the 309's drum sections. Let's be clear, though: you do not get two extra sequence tracks, just two extra synth voices.Each synth has all the programmability the 309 has to offer, and tweaks can be made from the front panel, and sent over MIDI or recorded into the dedicated Master track). Press and hold F1 or F2 (under the display), and you can use the bass/lead synth's controls. For more detailed editing, double-pressing F1 or F2 takes you to the main editing pages, visible on the display."
