Then riding a wave of successive Top 40 hits, in 1973-74 the band Chicago appeared in two televised specials, “Chicago in the Rockies” and “Back at the Ranch.” Both were shot at the beautiful Caribou Ranch in Nederland, Colorado, where Chicago and other notable bands of that era retreated to record some of their finest work (among many others, Elton John’s album Caribou was laid down there). The format of both programs was largely the same: Chicago played their hits live for fans and invited some of their heroes to join them. One special such guest was the legendary Al Green, a chart topper himself at the time, with whom they made a little magic.
We feature here Chicago supporting Green on his hit “Tired of Being Alone” and on their own track “Call On Me.” While known primarily for their particular brand of jazzy, soft rock and pop, the band clearly also had an affinity for soul/R&B music.
source: Flashback Soul