I remember Chicago's albums were just numbered although they brought out a four disc live at Carnegie Hall album which will cost you £100 on CD or a tenner as a download here, when a double album as considered stretching it a bit. Also I believe guitarist Terry Kath lost his life playing Russian Roulette.
I was never a big fan of the band apart from this single and when they hit their wimp rock phase they were way past their sell by date for me.
I suggest you research what I've told because it has all just come from my head so maybe needs taking with a pinch of salt, but enjoy this and if you want to really check out Chicago check out their early stuff and expect some serious brass. I found an excellent live take from 1970, and yes I would have gone and seen they , plus you get a brilliant guitar solo from Terry Kath.
Enjoy your Sunday night my friends.