Sentence without commas:

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

Sentence with two commas:

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

The two commas are absolutely unnecessary.

Now bugger off like a good little fellow.