via this auction
"Green aluminum case + extra sound.
The Pocket Piano GR is the same great instrument as the regular Pocket Piano with an added special mode! In addition to the six sound modes of the standard piano, the GR has a seventh mode: a monophonic 4 oscillator beating synthesizer with glide. 7 modes total:
• Vibrato Synth
• Harmonic Sweeper
• Two-Octave Arpeggiator
• Octave Cascade
• Mono FM Synth
• FM Arpeggiator
• MONO GLIDER
GReat new sound for low phasing glides like a prop plane and distorted 'mid-leads' soloing.
Green anodized aluminum enclosure, wood keys, powered by 9V battery or a9VDC Power Supply, 1/4" output jack, built-in 3-watt speaker."
