The 1960s were the age of the flowering of electric instruments. Bob Dylan had gone electric in 1965, but jazz had gone from being progressive music in the 20s to being far more conservative in the 60s, resiting in particular the call of electric instruments.
In 1968, jazz was dying a slow death in the face of Rock and Roll, when jazz innovator Miles Davis went electric. He revised jazz from its increasingly conservative roots, and virtually single-handedly invented jazz-rock fusion.
Here is one of my favorite tunes is this period in Miles’ life. It is from the album Bitches Brew, and is called Spanish Key. The song is 17 minutes long, so it had to be divided into two halves on YouTube. Enjoy.