A leftover cylindrical potato chip can and some card stock make a do-it-yourself trombone that will help your students learn about pitch. Wrap the chip can snuggly with card stock to form a sleeve around the can that fits tightly, but can slip up and down. Show your students the sound the can makes when you tap it with the sleeve all the way on. Then slide the sleeve down as far as you can and tap the can again. Students will hear a much deeper tone as the sound is affected by running down the paper tube. This is the same reason deeper sounds come from a fully-extended trombone.
If your students have ever heard the sea by holding a seashell to their ears, they have experienced resonance. The shell reflects the sound of their own blood rushing back to their drum. Set up an experiment so your students can test how the pitch of resonance is affected by the size of the vessel held to their ear. Collect glass jars in different sizes. Have students hold each to their ears so that they can hear the differences in pitch.
A small piece of dry ice tied inside a rubber balloon will fill the balloon with carbon dioxide and give you a tool for a lesson on volume. Sound travels more slowly through carbon dioxide than it does through air. This, combined with the shape of the balloon, focuses sound. Have students stand with a carbon dioxide filled balloon between them and whisper to each other. Their voices will be amplified.
Sound travels more efficiently through solid objects than air. Your students might not believe you when you tell them that, but you can prove it with an experiment. Tie a long piece of string to the top curve of a wire hanger. Wrap the other end of the string several times around a student's index finger and have them swing the hanger so it hits a metal surface such as the side of a desk or filing cabinet or chair leg. This will produce a dull sound. Now have them cover their ears with their hands and lean over so they can swing the hanger into the surface again. This time the sound will be more harmonious, because it is traveling up the string, through their hand and directly to the ears rather than through air into the ear.