I was trying to play a cheap Casio keyboard along with one of the music channels and couldn't find the key. I seemed to be halfway between two keys, like the keyboard had gone a quarter tone sharp. The keyboard was a CT-650 of unknown age I got free at a yard sale.

So I dug out a couple more, an ancient CTK-650 I've had for decades and a new CTK-700 I bought when I'd moved and had nothing available. (Yes, I have a decent DP I use for practice, I'm just accumulating cheap keyboards with a MIDI out to use for a software organ I want to build)

Anyway, two nearly identical Casio keyboards are in tune with each other and with the cable tv, and the third keyboard is a quarter tone sharp. I tried with and without batteries, swapping power supplies, etc. The one keyboard is always sharp.

Any ideas?

Go with Fischer-Price next time?

You get what you pay for, I guess. Unless it has a sophisticated tuning adjustment you can make, which I doubt.

Most digital pianos can be adjusted so that A=440Hz or any other value within reason. Sounds like somehow yours got set a few "cents" off.

The keyboard can also be transposed but that happens in full semi-tones so that can't be the problem.

Try a factory reset or setting back to 440

Does the keyboard have a tuning or pitch control?

Snazzy

Just for fun, call a piano tuner. Some might need a good laugh ;)j/k of course

Googled around a bit, but it looks rather difficult to find a manual for that model online. If you have one, though, tuning or pitch control is definitely what you'd be looking for.

Go into the tuning function and set it to A=440. I found one in a music store out of tune with the other dp's, and discovered how to tune it - it's intuitive - just poke a few buttons 'till you find it.

If it's a cheap 61 key Casio, it probably doesn't have a way to adjust the tuning. Some of them might, but a lot do not. You're probably stuck wth it like it is.

One more idea. Does it have a pitch bend wheel? If so the wheel could be bad and not re-centering itself perfectly

There is no obvious reset or tuning function, but I'll play with it tonight and see if some button combination does something. There is no display of any kind.

I wonder what MIDI puts out? Would that be tuned as well?

That would be interesting to know. If anything, you could just use it as a MIDI controller but you'd have to adjust the pitch after recording, which seems to be a lot of work for a cheap instrument, when you have others that would do a better job.

A cheap keyboard can be a substitute organ manual, feeding MIDI to a software organ emulation. Obviously I need a minimum of three, and one has to be converted to handle input from the pedals. So I watch for them at yard sales, but I'm not willing to pay much.