Until the Beatles, it was all just rock-and-roll. But with their later albums, starting with Rubber Soul in 1965, they blew the music up from the inside. We got psychedelic, progressive, southern and fusion rock and then even more. The earliest examples of fusion were basically adding some jazz elements – essentially horns – to the music. And the earliest examples were Blood, Sweat and Tears and Chicago. Chicago first appeared as the Chicago Transit Authority in 1969 with the album of the same name. After Chicago’s first three albums, the band began becoming a sort of stereotype of itself. But I still listen to the first two, especially when driving. Try Beginnings, from CTA. It opens with acoustic guitar, adds horns and vocals and ends with a riff of what sounds like marimbas and cow bells. It wasn’t just R&R anymore.