What Sayid and Hurley were listening to was The Others giving their memorial service to either Ethan or Goodwin. We know they play music when someone is being remembered because they did it at Colleen's funeral
Since Ben phoned the freighter to contact Michael means that he ordered Bonnie and Greta to turn the jamming off for a while. This means that Hurley and Sayid may have listened to "Moonlight Serenade" while the jamming was switched off during a call Ben made. (Like contacting Richard on the mainland). Then the signal went out because he ordered the ladies to switch it back on.