Spanish soprano Montserrat Caballé, with whom Mercury recorded an album, expressed her opinion that “the difference between Freddie and almost all the other rock stars was that he was selling the voice.” She adds,his technique was astonishing. No problem of tempo, he sung with an incisive sense of rhythm, his vocal placement was very good and he was able to glide effortlessly from a register to another. He also had a great musicality. His phrasing was subtle, delicate and sweet or energetic and slamming. He was able to find the right colouring or expressive nuance for each word.