There’s an interview of great ghazal singer Mehdi Hassan on YouTube in which he talks about the effortlessness with which he was able to embellish his songs with khatkas and murkis but when, as part of his training, he was asked to hit the notes straight, he found singing really hard. ‘Khade Sur’, he said, were the most difficult to get right and it was only by constant practice in this department that he eventually got as far as he did.