Depending on the type of group I was playing with, I would use a Yamaha CS-01 Synthesizer as a strap on...small, mini key and great analog sound...and it had a breath controller!
It didn't have MIDI but its own sound was quite fat and rich...monophonic only, but a super lead synth.
Great for bass...it had a 32' oscillator setting.
I still have it.
I also used a Casio CZ-1000 as a strap on...never used the MIDI, but, like the CS-01, it wasn't needed...the sound was great.
The CZ-1000 was also 8 note polyphonic so I could comp on it as well, although it sounded better in double or stacked mode with the resultant loss in poly(down to four).
The keys, unfortunately were not velocity/after-touch sensitive, but they were full size and the instrument was very light and easy to use in the strap on position.
It had a wicked feedback guitar patch.
Ian
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Common misconception...size and weight equal quality and performance. Don't be fooled.
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.