lost the internal speakers

on my macbk os 10.12.6, I was making an overdubbed recording and lost sound both on the headphones and the internal speakers. so no audio on mcbk. I was able to recover the sound through the headphones but no sound from the computer.How can I fix this?

Uh, reboot?

Actually, I am not quite clear what you are asking. Note that in most cases when overdubbing, you should be using headphones and not speakers (internal or otherwise).