Singing and playing really can help you to improve your sound. Once you get the hang of it, you will improve. Remember that only working on the techniques, even if it feels you’re unsuccessful, will help you improve. You can adjust the level of this piece. Start by singing and playing simultaneously. Mind the intonation. In the second level sing the second (voice) part and play the flute part. Practise slowly. And for those who need challenge, sing and play the two parts at letter B. After studying the singing and playing, play the piece without singing and notice the difference!