One side effect of the recent electronic dance-music boom has been that calling yourself a DJ is a now perfectly respectable thing in its own right. You don't really need to be a hyphenate—say, a model-actor-DJ—anymore.

But try explaining that to Jan Gunnar Solli, the fullback-DJ: The 31-year-old Norwegian plays for the New York Red Bulls of the MLS by day and has a DJ residency spinning at the nightclub Pink Elephant on Eighth Street by night.

Mr....