This is a post that will satisfy synth geeks and very few others.
I recently bought a keytar, a Yamaha SHS-200 to be precise. It was a wonderful eBay purchase - bought for a song (pun intended) and in absolutely mint condition.
I really bought it for a laugh, but last Sunday at C3 we had a bassist crisis (they were all either playing guitar, busy, studying, dead, or something) and so we needed someone (a keyboardist) to fill in for our lack of bassists. Hang on, I've got just the right implement for that job... enter the keytar!
So there I was, on stage, playing an 80s retro throwback instrument. Genius! Despite my lurking doubts, the whole thing went really well. I was able to play some great bass parts, and doing so on the keytar was ace - I had room to move around, and wasn't constrained by being behind a large keyboard (which just doesn't make sense when you're trying to play bass parts). I normally move around quite a bit when playing keys, but there's a limit to how far you can move without a keytar.
The proof of the playability was in our opening song (Salvation is Here). It has a bass solo in the middle of it (check it out 2:20 in that video), which the keytar handled excellently. Much more fun to play than on my normal RD-700sx.
The Yamaha keytars are a bit limited compared the their obvious Roland counterparts, and it took a little getting used to. The keys are mini-sized things, and so are a bit fiddly to play, but once you're used to them you can play long bass runs without moving your hand too much. Useful.
The Yamaha beasts are not touch sensitive, which looked like it was going to be a real limitation. However, it turned out not to matter that much at all; in the majority of the songs you wouldn't have noticed anyway. This was only really a problem in quiet parts, when I had to modify what I'd play slightly. It did require some handling care, though: being small, light keys, it's also very easy to hit notes by mistake, or with your palm.
I only used the device as a MIDI master, and run the sounds from my normal rig. This is a serious retro instrument, and 80s FM bass honks would not have been appropriate!
All in all, it was great fun to play the thing live.
Keytars are going through a bit of a revival right now. I don't know why. Let's be honest, they're wrong in almost all important respects. They look silly. Any they make people squint at you like you're a lunatic. Using a keytar is just another way of asking for ridicule. But playing one is a very dirty kind of pleasure.
For those dull enough to care, more interesting keytar porn can be found here and here.