CREATE TABLE vocals (bandmate VARCHAR)
CREATE TABLE band (id VARCHAR)

Which vocal type has the band mate with last name 'Heilo' played the most?
SELECT TYPE FROM vocals AS T1 JOIN band AS T2 ON T1.bandmate = T2.id WHERE lastname = "Heilo" GROUP BY TYPE ORDER BY COUNT(*) DESC LIMIT 1
SELECT "TYPE" FROM "vocals" AS "T1" JOIN "band" AS "T2" ON "T1"."bandmate" = "T2"."id" WHERE "Heilo" = "lastname" GROUP BY "TYPE" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1