in recording studios!
if the origonal tape on the reel to reel cuts or gets jammed or some how the recorder breaks down, you always got another recorder with the "saftey tape" in as back up, one of stevie ray vaughans albums was recorded on stevie wonders saftey tape for his layers of love album.
jimbo the gonnabe famous:oh no the recorders stopped recording halway through my song,
dave the studio owner: oh its ok keep goin don't worry, the saftey tapes there, its alright, we got it.
jimbo:oh crickey thank the good lord.