Bollywood superstar Salman Khan has sung for his films in the past, but he says recording a number for "Kick" took him as long as three days. The actor says composer Wajid of his favourite Sajid-Wajid duo was his guru and he just followed his instructions. "I have sung in 'Hello Brother' and 'Wanted' also. People around me have been asking me to sing a song in a film and my problem is I can't do it if anybody asks me to...it has to come naturally," Salman said here. He found the experience tough. "Singing in front of the mike is very difficult without any training. I am not a trained singer at all. Wajid used to sing in front of me, and I used to copy. My guru is Wajid," he added. Salman, who stars in "Kick" with Jacqueline Fernandes, says the song sounded "bad" once he recorded it. "Once it was complete, it was sounding very bad. But the composers were saying, 'It's superb, don't worry'. They were confident about their technicians and said the song will get refined and by the time it comes out, it's going to be 70 percent better. "Usually, a trained singer does it (records a song) in an hour or so. I took three days," he quipped.