This option also works well when the two clauses are of equal importance. In a run-on, add a semicolon. In a comma splice, replace the comma with a semicolon:

The band has just three other members; they play different instruments on different tracks.

To clarify the relationship between the ideas in the two clauses, consider adding a transition word or phrase, such as in contrast or meanwhile, to the second clause, followed by a comma:

The band has just three other members; however, they play different instruments on different tracks.