As with the CompleteAllQuestStages command - this command may cause bugs, so it is recommended that you first save your game. This console command completes the quest with the specified ID.
completequest [quest id]
|Quest ID||The quest ID of the quest you wish to complete.|
Rjorn's Drum has a quest ID of BardsCollegeDrum. This command would complete the quest Rjorn's Drum.