There was a station I used to listen to in the '70s that was Classic Rock (ok...back then it was AOR) on the FM side and Top 40 on the AM side. Both stations carried the same local newscast, which was promptly started at the TOH. The AM and FM stations, with their independent formats, would simulcast the same song that lead to the TOH.
Thus, the FM DJ would tell the AM DJ that he's going to play (for example) Lido Shuffle at :56.20 and has a :06 intro. Both the AM and FM DJs had to backtime their shows to simultaneously hit the :56.20 start of Lido Shuffle. I witnessed it once as a guest in the FM studio. I was in awe.
dr
Thus, the FM DJ would tell the AM DJ that he's going to play (for example) Lido Shuffle at :56.20 and has a :06 intro. Both the AM and FM DJs had to backtime their shows to simultaneously hit the :56.20 start of Lido Shuffle. I witnessed it once as a guest in the FM studio. I was in awe.
dr