#1
I was wondering if someone were to play a keyboard through my guitar amp...just for one practice...if that would be harmful to my amp

I heard that it could possibly hurt the speakers because the frequency a keyboard puts out is so much lower
#2
It won't hurt your amp, but it will sound a bit weird.

Opeth do it live, so it cant be that bad.
A metal band?
Gear:
A Guitar with an LFR > Korg Pitchblack > Behringer EQ > Hardwire CM-2 Overdrive Boss SD-1 > Hardwire CR-7 Chorus>
Orange Tiny Terror >
LzR Engineering 212 cab

My other amp can run Crysis
#3
depends on what keys you use lol, if youve got a modelling amp etc or an amp with plenty of FX built in i dont think it wont be bad lol
#4
ok i was just wondering
it freaks me out when I think about hurting my amp haha..