Azimuth recording

Azimuth recording tilts the write head's gap by a few degrees, alternating direction on neighbouring tracks. When the read head then follows a track written with "its" tilt, it reads that track strongly but the neighbour's skewed pattern only as faint noise, because a gap reads a track of the wrong azimuth very poorly. That let designers drop the guard bands between tracks and pack them tight against each other — more data on the same tape.

The technique came from the video cassette recorder; Betamax and VHS used it on their helical scans, and it was inherited by digital tapes that recorded with rotating heads, such as DAT and 8 mm. The price is that the tape has to be read with the right head and can't tolerate coarse tracking.