Lupu was born in Galați, Romania on 30 November 1945, the son of Meyer Lupu, an attorney, and Ana Gabor, a linguist. From his earliest days, Lupu "had always expressed himself by singing", and was given his first piano at the age of 5. He began piano studies in 1951, as a six-year-old, with Lia Busuioceanu. He made his public debut in 1957, at age 12, in a concert featuring his own compositions. He told "The Christian Science Monitor" in 1970 that "from the very beginning I regarded myself as a composer. I was sure, and everybody else was sure, that one day I would become a famous composer". He gave up composing about four years later, saying that he thought he would be "much better as a pianist".