What he say
DO NOT PLAY INSTRUMENTS THROUGH NON-INSTRUMENT SPEAKERS !
Warped woofers, blown tweeters are common gripes
It's the transients that an instrument speaker doesn't respond to, and that a playback speaker does, which will do them in.
The amp doesn't care as much.
But "design for purpose" will ultimately matter
FWIW, I still tune mine by "singing" "my-dog-has-fleas", which I was taught at 4y.o. with my first little plastic Uke
The tuners were plastic, so I sang that a lot :-)