So forgive me the topic I mention has been discussed.
Probably one of their fist big hits was 25 or 6 to 4.
But one thing that's interesting is the melody for it resembles a Led Zeppelin song "Babe I'm Gonna Leave you."
Since LZ released their first LP in 69 the same year Chicago released their first and 25 was off Chicago II in 1970 one can't help but feel Chicago did borrow that sound from "Babe."
But as we know Chicago formed in 1967 and who knows how old many of these songs were. My understanding "Wake Up Sunshine was written in 67 and didn't get recorded till Chicago II.
Matter of fact this is a live recording which says it was made in 1968. LZ formed that year but as I said before their fist release was the following year so is it just a coincidence that both "Babe" and "25" sound alike?
Also check out this video of