The Vocalizer was a small module designed as a pitch to synth converter and built around the Ensoniq Q chip. While only marginally effective as a pitch to MIDI converter, it does have the same soundset as the Ensoniq ESQ-1 but without the analog filters. The unit has sixteen note polyphony and responds to all sixteen MIDI channels. It is not possiblee to restrict MIDI response to only a few channels, making the module inconvenient to use without a MIDI filter. The unit responds to MIDI volume , pan, and program changes, the latter being the only way to select sounds on channels 2 - 16. The Vocalizer features the same waveform set as the Ensoniq ESQ-1, which means you get the same grungy basses, pianos, and synth sounds. The lack of analog filters is a dissappointment, but considering the unit's original sub-$400 price tag, not suprising. A cartridge slot is tucked away inside the battery compartment and appears to have the same form factor as ESQ cartridges, but is not compatible. ROM carts were available from Voice Crystal for a short time, long since discontinued. The Vocalizer pales in comparison to today's synthesizers, but in 1990, was a great expansion to my single Casio keyboard sound palette.