Not that I'm a fiend stealing bass like Otis Nixon
Otis Nixon was a famous baseball player, most famous for his record in which he now shares for stealing bases. Shad refers this to the word bass, instead of base, where he is talking about the musical instrument.
Base (bass) is a triple-entendre here, since it also refers to free-base cocaine, which a “fiend” would likely try to steal.
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