There are apps to correct the tune in songs. At times, even an established singer suffers from respiratory distress and is on antibiotics. In such situations, the technology helps. However, it is not correct to depend solely on technology to record a song. At times, a professional singer feels like redoing a line. The recordist has Melodyne, an audio pitch modification tool. It could be used, rather than reading a line or two. However, the output clearly shows that the song has gone through a processor and sounds metallic and/or unreal. There are singers who have capacity to sing without using technology. It requires practice or riyaz. It is of primary importance to a singer. Film songs contain phrases on the beat. They are rhythmically not complicated. Previously, if a singer was off-key, or was unable to catch a beat, the only option was redoing since the tools and apps did not exist then.