Another example where the comma before 'and' will obviate a possible ambiguity or misunderstanding:-

"The company's repertoire will consist of light operas and musical comedies by Lehar, Gilbert and Sullivan, Friml, and Rodgers and Hammerstein."

In Eliza's above example, I think the greatest aid to understanding would be commas both before and after the 'and'. {Read it aloud, and feel how the cadence suggests this double comma. Indeed, reading aloud, and feeling where a momentary pause is implied, can often be helpful.}

~M~