Get in touch with your voice and your ear. Sing as you compose and find the tones through what you sing. Playing the piano (or some other instrument) will, of course, help develop your ear, but your main aim should be to get the music in your ear and voice as well as in your mind and fingers. Learn to sing, tone by tone, what you compose, while you are composing it. You should also be able to sing the completed series of tones.