That blurry-sounding guitar line that leads the Beatles' "Think for Yourself" from 1965's Rubber Soul? That's actually no guitar at all.
It's a bass part, played by Paul McCartney and fed through a device called a fuzz box, which creates a kind of grainy, distorted effect. (There's a regular bass part, too.)
And as with many Beatles tracks, it broke new ground — "Think for Yourself," written by George Harrison, marked the first time this device was used on purpose with a bass.
'Don't Worry' and 'Zip-a-Dee-Doo-Dah'
Four years prior in 1961, a similar sound was created in Marty Robbins' "Don't Worry," a huge No. 1 hit on the country chart. But in that case, the fuzzy bass sound was essentially made on accident, the result of some kind of technical malfunction that Robbins' ultimately decided to keep on the track.
A year after that, producer Phil Spector helped Bob B. Soxx & the Blue Jeans achieve something similar on their cover of "Zip-a-Dee-Doo-Dah." According to Harrison, who worked with Spector on a number of occasions after the Beatles split up, it was a makeshift thing.
"When Phil Spector was making 'Zip-A-Dee-Doo-Dah,' the engineer who's set up the track overloaded the microphone on the guitar player and it became very distorted," he said for Anthology. "Phil Spector said, 'Leave it like that, it's great.'"
Source: ultimateclassicrock.com/Allison Rapp