DD9 asked to play the flute since age 5. I offered piano (my instrument) or violin, but she had no interest. I called a music school when she was 6 and they said to wait until 7. When she turned 7 we began flute lessons once a week and discovered that she could read music. She like playing but isn't always disciplined to practice as recommended. Her teacher is easy going and we advance at a comfortable pace, faster or slower depending on other commitments.
I grew up in a musical family and starting an instrument/age depends on a lot of factors. The instrument for one, some can be mastered earlier than others. Flute takes great coordination of breathing and finger dexterity. It can be frustrating to try to make a sound for weeks and then figuring out fingering for each note vs. instant sound of pressing a piano key.
Since the OPs DS is 4, I would suggest a group music lesson at first to see interest. Also, allow your child to try different instruments and see what interests him. Suzuki is a group lesson but in its true form it is a big commitment and not a great fit for everyone. Our DS3.5 is asking for a violin, but I wouldn't think Suzuki would be right for him. Plus I can't imagine sitting in a room full of beginners listening to all that screeching, LOL!!!
