This is Jerry Farmer, instructor of Radio TV at CCCC inserting a 4 track cartridge into the machine. Four track were used to play commercials and public service announcements. Some carts are 2.5 minutes; 3.5 minutes; 4.5 minutes; and 5.5 minutes. These are long enough to record songs on them in order to preserve the 45 rpm records. The longest regular sized cart to fit into the machine Mr. Farmer is using would be 10.5 minutes which is long enough to record: Gordon Lightfoot's the Wreck of the Edmund Fitzgerald from 1976; Don McLean's American Pie from 1971; and The Temptations' Papa was a Rolling Stone from 1972. All three of these songs exceed six minutes in length. [description provided by Dr. Anthony Ross Harrington]