Keith Richards recalls the effect of portable cassette recording on his music, part of a new tribute to the just-discontinued Walkman by my friend and historian of popular technology Phil Patton, at designobserver.com:

Just as turntables influenced the birth of hip hop, the often overlooked cassette player helped in song writing and affected the way he played the guitar.

"I'd discovered a new sound I could get out of acoustic guitar," he writes. "That grinding dirty sound came out of these crummy little motels where the only thing you had to record with was this new invention called the cassette recorder....Suddenly you had a very mini studio. Playing acoustic, you'd overload the Philips cassette player to the point of distortion so that when it played back it was effectively an electric guitar. You were using the cassette player as pick up and amplifier at the same time. We were forcing acoustic guitars through a cassette player, and what came out the other end was electric as hell."

One precedent not mentioned: Bing Crosby's development of the crooning style made possible by the introduction of the electric microphone in 1926, which freed recording singers from the tyranny of having to shout into an old-style horn. Especially in the arts, it's nice to be reminded of positive unintended consequences.