Short for Reproduction, the repro function in tape recorders allows for the playback of all tracks, including those that are currently being recorded. The way this works is through the use of a separate repro head. The repro head of a tape machine is generally only capable of playback (not recording) and is optimized as such. In the earlier days of tape recorders the repro head was the only head on a tape machine capable of full fidelity playback. It usually has its own set of corresponding electronics in the machine that can also be optimized for playback. Also important is the positioning of the head, which is after the other tape heads along the tape path. Since the repro head is last in the series, the engineer can monitor off of this head even while recording on another head, which means it’s possible to literally monitor the actual results of the recorded (and played back) signal on the tape. This is sometimes also referred to as confidence monitoring. The only caveat is that the signal one hears is delayed by the length of time it takes a particular point on the tape to travel from the head where it was recorded over to this separate repro head. This distance is usually not much more than an inch and a half, so if the tape were moving at 15 ips the delay would be about a tenth of a second.