How many different songs have shared vocals?
SELECT count(DISTINCT title) FROM vocals AS T1 JOIN songs AS T2 ON T1.songid  =  T2.songid WHERE TYPE  =  "shared"
SELECT count(DISTINCT title) FROM vocals AS T1 JOIN songs AS T2 ON T1.songid  =  T2.songid WHERE TYPE  =  "shared"
[{'count(DISTINCT title)': 0}]