Asking an elective professor?

[AHGRE]

Would it be appropriate to get a letter of rec from a professor that I took an upper div elective with? I already have two recs from profs that I took my major classes with.

[emmm]

Was the elective relevant to your area of study? Can the professor comment on more than just your performance in the class?

[practical cat]

I think relevancy really matters. If you're applying for science-type programs and are thinking about an English professor, I would say probably not. But if they can comment on your work in a way that adds something meaningful to your application and having a professor from a related field would help give a clearer picture on the kind of work you would do, maybe. But overall, I'm not really sure that a letter from someone you took one class with in a different field would be any stronger than a letter from someone you took one class with in your own field.