Complex sentence: When Kosenko was about five or six, he began to pick out familiar melodies on the piano, had absolute pitch, a good musical memory, and would attempt to improvise, already showing signs of his musical potential early on.
Split into simpler sentences: When Kosenko was about five or six, he began to pick out familiar melodies on the piano, once he had absolute pitch, and a good musical memory. He would attempt to improvise, showing signs of his musical potential early on.