What is the last name of the musician that has been at the back position the most?
SELECT T2.lastname FROM Performance AS T1 JOIN Band AS T2 ON T1.bandmate  =  T2.id WHERE stageposition  =  "back" GROUP BY lastname ORDER BY count(*) DESC LIMIT 1
SELECT T2.lastname FROM Performance AS T1 JOIN Band AS T2 ON T1.bandmate  =  T2.id WHERE stageposition  =  "back" GROUP BY lastname ORDER BY count(*) DESC LIMIT 1
[{'Nenhum': 'Nenhum resultado encontrado'}]