An analog tape head configuration consisting of four tracks. Some quarter track machines are configured to be four track recorders, but most machines intended for consumer use are set up to be two track (stereo) recorders where the tape can be recorded in both directions (two tracks one way, and two the other). In reel-to-reel tape machine configurations, where the terms quarter track, half-track, and full track are most used, getting access to the other two tracks requires turning the tape over, which on a reel-to-reel can be a bit cumbersome to do. Generally speaking, tapes with a given number of tracks recorded on them are only compatible with corresponding head configurations; however, some head stacks have been made over the years which can switch between half track and quarter track operation.