With some creative use of the memory window in debug mode you might be able to softlock or otherwise delay parts of the game.
You mentioned Data East games from the 80's. In Karate Champ VS, address $CF02 is the timer for the high score initials entry screen. If you set it to 99 seconds that gives more than enough time to hear the whole song, which you otherwise wouldn't be able to hear in the 30 seconds it gives you.
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