What was the first rock band to use tape loops?

Tape loops appear to have been used in the late 1950's by the BBC
http://www.absoluteastronomy.com/topics/Tape_loop

and then by classical composers Terry Riley and Steve Reichs
http://www.loopers-delight.com/history/Loophist.html

but the earliest record I can find of a rock band using tape loops is of the Beatles in 1966. The most poignant example being the track 'Tomorrow Never Knows' off the Revolver album.
https://en.wikipedia.org/wiki/Tomorrow_Never_Knows

Depending on a person’s definition of rock band (many consider The Beatles to be a pop band.) The answer would be Fifty Foot Hose.

Beginning in the late 1950s the BBC Radiophonic Workshop began using tape loops to add special effects to some BBC programming. Pop musicians, most notably The Beatles, Frank Zappa, Fifty Foot Hose, Can and Pink Floyd have used tape loops on their albums.
In the early 1970s, musicians Brian Eno and Robert Fripp created Frippertronics, a system for creating tape loops during a live performance.
Digital loops overtook much tape loop use, beginning in the mid 1980s.
http://www.absoluteastronomy.com/topics/Tape_loop