After many years of thinking about it, I finally pulled the trigger on a Korg X-911. It was a very early foray into guitar synths, the only one I'm aware of that you can use without a custom pickup. It detects an input frequency (monophonic only unless you want it freak out and glitch, in which case play chords by all means) then uses that to trigger a series of oscillators. There are 5 "instrument" presets which have 4 low pass filters and one simple envelope generator, and 6 "synth" voices that have envelope generators. Plus a main low pass filter, pitch shift, input sensitivity and output volume. It also outputs the main guitar signal, and can be used as a processor sending guitar thru a simple distortion circuit or the LPF. On mine the "guitar thru LPF circuit" isn't working. So, how does it sound? The individual voices can be useful, for example set at -1 octaves and using a 16' voice or two gives you a nice bass. Plus combining the filters and the envelope generators means that you can have some movement to the sound. You can mix the Instrument and Synth voices as blocks, but not individually. More interest probably happens for a guitar lover like me combining some of the smoother voices with some of the raunchier ones. It can be fat and juicy, thin and skanky or pretty thick and hard edged. Basically an MS20 synth driven by guitar. Oh, and it does track decently if you're careful about gain staging, use the neck pickup and keep your attack even (or compress your guitar signal). There's lots of connectivity for CV/gate in and out, as well as ways to turn the features on/off and an infinite hold switch. All in all a pretty full featured "pedal". But wait, there's more! Since it detects incoming pitch and does its magic from there, you can send it basses, drums, keys, even voices to process. Some of the stuff on youtube shows it being used as an extra voice/filter for analog synths (they don't even have to use the Korg volts/Hz signal, since you're driving the X-911 with the pitch of the synth, not its CV). I'm looking forward to delving into this more fully. Apparently this was the basis for the Pigtronix Mothership, another cool guitar processor, although a little more conventional and without the many voices.