Here are some real simple instruments you can do without hassle:
I found a discarded wicker laundry basket in the trash a few years ago. I took it to my shop and carefully disassembled it, saving the wicker pieces in a cardboard box. In a workshop the following year, my students cut the pieces into uniform lengths, bundled them together and bound one end with rubber bands, making a sort of brush:
When tapped or shaken, they made a fine rattly-brushy percussive sound.
Save plastic water or juice bottles. Rinse them and let them dry. Put in a handful of rice or beans. Different amounts of different materials give different sounds; a garbonzo rattle sounds nothing like a rice rattle. If you want to get fancier, a cut-off piece of broomstick can be made to fit in the neck of the bottle (epoxy is sometimes necessary, but often a friction fit is fine). Kids enjoy decorating these rattles.
Plastic water bottles can be partially filled with water to change the amount of air space inside. This allows you to tune them to different pitches and create an ensemble of one-note flutes that has the potential for a richly hypnotic groove. Here’s a whole classroom jamming on water bottle flutes and rattles — and two frame drums to add sonic variety:
Different sizes of tin cans give different sounds, and you can make quite an effective “steel band” by putting together an ensemble of people playing different parts on their various cans. Mallets are useful for tin-can instruments; use the string-soaked-in-glue to make harder mallets, or drill a hole in a bouncy ball to make a bouncier mallet.
Any kind of tubes (cardboard, plastic, metal) are a fabulous source of music. I often use the plastic tubes that are used protect flourescent lightbulbs in many industrial situations.
Cardboard tubes from shipping contexts are excellent, but you can’t hit them together or they’ll break. Glue a little piece of plywood across one end, and the closed tube will make a very satisfying pitched sound when you tunk it on the floor. Varying lengths yield different pitches, the longer the lower. You can distribute them to your friends at your next party and have a fabulous jam session…