 The musicians recorded ten takes , the last of which was selected for overdubbing . To create what Spector biographer Mark Ribowsky terms a " four @-@ man Wall of Sound " production , Lennon added grand piano onto the basic track , while Harrison and White shared another piano and Voormann played electric piano . In addition , Beatles aide Mal Evans overdubbed chimes ( or tubular bells ) and White added a second , muffled drum part . With Lennon feeling that the chorus was missing something , Preston and Evans were sent to bring in a group of people from a nightclub to provide backing vocals . These newcomers and all the musicians , along with Allen Klein , then added chorus vocals , with Harrison directing the singing . 
