I can’t remember if the tape drive came with a TRS-80, but I do remember using the tape drive port to get sound from games like pacman. Basically it was hack to use the save to cassette to make sounds for the computer.

This game contains programming which produces sound effects that leave the computer through the AUX plug in the cassette cable. To hear the sound follow these instructions: First, load in the game. Remove the tape from the recorder if you loaded the game from cassette. Insert the large grey plug on the cassette cable into the AUX jack on the recorder. Insert an earphone into the jack labeled EAR on the recorder. Pop open the cassette door on the top of the recorder and reach in and hold in the interlock switch that is located in the left rear corner. Now press Record & Play together and then release the interlock switch. Sound should now come through the earphone.