How to uninstall and re-install garageband

On which device do you want to reinstall GarageBand? A Mac? An iPhone? An iPad?

And on which system version? The version you need for reinstalling may no longer be available at the App Store, so you should make a backup before uninstalling.

What is the problem you need to fix?

I am a neophyte to garage band so I am running into glitches, where what I am recording using a USB interface on my MacBook air I can hear what I recorded on playback, and It seems that my I phone see 2nd gen is overtaking the microphone or input even thought I go back to settings to reset it. Very frustrating. Also the tuner acts like its on drugs. I read that deleting garage band then reinstalling it can help but I have been unsuccessful doing that. Help!

Also it seems this issue has been somewhat episodic or intermittent.

Again, what device, is this a Mac or iDevice?