Usage and Grammar

Q. I work as an assistant editor, and I’ve been having trouble with the phrase “as well as.” In some sentences, it means “in addition to,” as in the sentence “I ate the burger as well as the fries.” In other cases, it is used as a form of comparison, as in “I play the guitar as well as the piano,” meaning that I play both instruments with equal skill. Is one of these uses incorrect?

A. The second usage isn’t incorrect, but it’s ambiguous, since it can also mean that you play both guitar and piano, even if your guitar playing sucks. So if that’s not what you mean, make it clear, e.g., “I play the guitar as well as I play the piano.”