If I'm not mistaken, rechargeable AA batteries are 1.2 volts not 1.5. That might not be enough for this device. And in any case rechargable AA batteries do not last as long as the same volume of an 18650.
I had no idea that the NiMH batteries can provide higher current. That might be useful for e.g. servos. I'll pick up some, thank you.
(More of a chance that a vintage one would have trouble with NiMH batteries, though)
Edit: And yes, the batteries were properly charged ))
I certainly haven’t seen a single new electronic music device that won’t work with rechargeable AAs in a good long time. I am not sure the market would tolerate it.
(I do remember being told that rechargeable AA batteries in certain guitar effects pedals subtly affected tone, but I am not sure how much I would believe it.)
https://www.facebook.com/Omnichord.Heaven/posts/pfbid02GPS3J...
Oh I am so tempted.