I like the idea of a xylophone type of instrument. You might rather use aluminum soda cans for your tone-bars. fill them with appropriate amounts of water, and then use mallets to hit them. The mallets can be made with pencils and a bit of yarn wound around the eraser end to create a ball.
Another type of musical instrument you can make from recycled items located at home is a percussion instrument much like a maraca. Fill an empty plastic water bottle with small gravel from the drive way, dry beans from the cabinet, or uncooked dry rice. Each item will offer a different level of percussive noise.
You can make a horn type of instrument by using garden hose and a funnel or a funnel end from a plastic soda bottle. You will need some duct tape to secure the pieces together and to make them air tight. You can make a primitive horn by simply using the soda bottle with the flat end cut off. Buzz your lips like making a raspberry sound against the narrow funnel end, and voila...noise!
Check out the videos in the links below for other interesting and creative ideas.