You teach them by exposing them to a variety of music, by filling your home, your car, your world with music. And,for Christians, I believe having them in worship service every time the doors are open to be a must. Church music, and "learning to play for church" is a world all unto it's own, so having your kids in this environment early on is essential. I learned to play well for altar time and flow well in that atmosphere simply because first of all, I was raised in it. I will take a person who plays this way - primarily by ear or flow - in the church, versus anyone who is simply classically trained because learning to play for church is all about learning to flow, but that's another subject for another day. Okay, when, when, when is our topic today...
Music lessons start as you rock your children to sleep and sing to them. My children still remember the songs I sang to them. Savanna remembers a lullaby song I always sang to her (that I wrote) called, "Mommy's happy girl". Jordan remembers being sick at Christmas one year, and I rocked him to sleep singing, "We Three Kings." Kids never forget and hold these kind of things dear in their storehouse of memories. Sometimes my kids even ask me for a command performance. They wouldn't want to admit it to most (but the kids don't read my blog so I'll tell you) that at times they'll still sit on my lap and I sing to them.
I first learned to play the piano listening to Happy Goodman Family records. My parents played them all the time. When I was a little girl, Vestal Goodman was my hero. I still remember as a little tiny girl getting up in front of the church singing, "I wouldn't take nothin' for my journey now". I would sit and play my little keyboard right along with Goodman records and people would comment how good I would do, playing right along with the music by ear. "How does she do that?" people would say.
My parents got a piano, signed me up for lessons and everything I was hearing in my head became easier for me to play as I actually had a teacher show me the fundamentals. At that point, it seemed like music just exploded out of me. Pretty much all I would have to do is hear a song once and I could go play the entire thing or even play a song as someone began singing it (without every hearing it first) just feeling where they are headed. If you have a child who shows a potential to play by ear, I really encourage you to get them lessons right away because I've seen the same thing happen many times in others who are gifted the same way. It will just come pouring out of them, as they learn just a few fundamentals.
Some of the best learners are teenagers who are motivated. Now, if your child is a teenager and has had no musical training and doesn't want any, he or she probably won't learn much. However, if they have an INTEREST, it is definitely NOT too late. Motivated teens are one of the biggest sources of energy and creativity on the planet! Just look at how fast they learn video games, computer codes, html, among many other things. Motivated teens are absolutely changing the world. And they can easily learn an instrument!
For the motivated, it is never too late to start music lessons. If you are 42 years old now and say, "I wish I would have had lessons..." if you are motivated, it's not too late to start. Children do learn anything quicker, however, motivated people have the ability to learn anything. Just look at adult missionaries who go to language school to learn a brand new language to go to their field. They might be middle age, but they are MOTIVATED, and motivation makes all the difference.
At whatever age your child is at, find out what instrument they are interested in and then let his or her motivation carry them in learning to play their instrument.