i had been working on intonation since i first played piano it was difficult for me at this time after i learnt violin and played it almost of the day playing among many songs reading many sheet music i started to think again what about my ear music originally is by ear then i began to work more with intonation at this point i played 5 whole songs by ear it was difficult at the beginning but it now like a game for me and i enjoy each moment on that game