Helical scan
Spinning heads on a tilted drum write diagonal tracks — high relative speed without racing the tape back and forth.
Instead of writing straight tracks along a fast-rushing tape, the heads sit on a rotating drum tilted against the slowly fed tape, so each sweep lays a short diagonal track at very high head-to-tape speed and tight packing. The technique was invented for video (VHS, Betamax) and then carried over to data: DAT/DDS, Exabyte's 8 mm and AIT.
The opposite is linear serpentine recording, as used by QIC, DLT and LTO. The price of the density is a mechanically delicate drum and wear where the head constantly scrapes the tape.