Musical activities offer some of the easiest ways to play with your child:
Babies: Strike up the band
Give your sitting-up child two wooden spoons. Then set out several objects in front of him to bang: blocks, empty boxes and milk jugs, a sturdy ceramic bowl. Sit beside him, turn on some music, and with your own wooden spoons show him how to strike the items in something similar to the rhythm of the music.
Toddlers: Follow the music
This spin on Follow the Leader teaches about tempo and scale. Put on some music with changing beats and a range of high and low notes. Classical often fits the bill (try Beethoven's Ninth or virtually anything by Aaron Copeland), but lots of rock and pop tunes do too, especially songs by the Beach Boys and the Beatles. Let your child mimic you as you reach high during high notes, fall down during low ones, and alternately crawl slowly or skip rapidly to a changing tempo. When she understands how your actions reflect the music, let her take over as leader. For more fun, you can both use a scarf to reach up and down with, or a set of maracas to shake to the beat.
Preschoolers: "Write" a song
Hang a three- or four-foot length of butcher paper on the wall. Give your child a washable marker and sing or play a recording of a familiar song -- a slower tune is best to start. With your own marker, show him how to move his to draw the music, going up and down with the pitch and the tempo. You can even keep another color marker uncapped and at the ready and alternate colors when the song changes tempo or direction. Let your child try to draw the music he hears and sing it back to you.
Grade-schoolers: Name that beat
This game challenges kids to clap out the rhythms of their favorite songs well enough that other players can recognize them. Each player gets three turns to try to clap out a tune before singing along with her claps and revealing the song. Simple childhood melodies, such as "Row, Row, Row Your Boat," work best.