I would like to record a sound - talking, say - and then record a separate sound on top of that sound so both are audible?

For example, I have a device on the tabletop recording. I say something and stop the recording. Then, I record again, a guitar playing. I'd like to be able to hear both in the final recording with zero interaction - no editing, buttons or interaction.

Is that possible?

I read it used to be possible by 'cutting the lead to the tape erase head' in an old book...

If you had a stereo tape recorder (depending upon the particular unit), you could record your 1st track on the left channel then record the 2nd track on the right channel. Then play both channels back. And as I say this, I am thinking of several possible problems.

Have you considered doing it digitally on a computer? There has to be an application for musicians to record multiple tracks.