For children from birth to 5 years old Kindermusik classes are highly recommended. The latest brain research has confirmed: purposeful musical activities stimulate the cognitive & language, social & emotional, as well as physical developments that all begin in the very first days of your child's life. Kindemusik is the world's leading music and movement program for children from birth to seven years.
By the age of 5 children have longer attention spans, can retain information and have the hand size and finger strength needed for playing. For most children younger than 6, we would recommend " Music for Little Mozarts " - piano, music and movement classes or " Kindermusik for the Young Child" program where children can explore vocal development, rhythm, notation, musical symbols, and authentic pre-keyboard, stringed and wind instruments. Usually kids are forced into private lessons before they are ready. It isn't the parent's fault - they're just trying to do what's best for their children. But the thing is, at 4 or 5 years old, a child really isn't ready to make a long-term commitment to one instrument. They don't have the experience to know what they're good at, and what they'll like. Also, at that age, music needs to be fun for them, and most private lessons just aren't. The Kindermusik for the Young Child or Music for Little Mozarts programs are really great because it covers everything your child needs to get a head start in music, while keeping everything fun.
As a general rule, most children could begin formal instrumental training (piano, violin, voice ect.) at the age of 6. For success in piano study, a child must demonstrate mental, physical, and emotional readiness. In a general way, readiness is linked to chronological age, but there is a great deal of variation.
For students who want to play guitar the best age to start : 7+ years. Guitar playing requires a fair amount of pressure on the fingertips from pressing on the strings, which may discourage younger students who also may not have the fine motor coordination necessary.