If you're looking for an extra challenge with your preschooler, start to talk about HOW the noises are being made. Is your new invention a percussion instrument or a wind instrument? Try drumming on three different sizes pots and discover the relationship between the size of an instrument and the sound that it makes.
If your child loves sounds and music, hunt down some YouTube clips of various instruments, or better yet invite yourself over to a musician-friend's house and let the kids see instruments in action! Nothing inspires a young musician by seeing music performed in front of them! Guitars are very common, but search around your community for other instruments your children can see live and then try to make one of your own at home!