A PVC trumpet serves as a demonstration piece for the “harmonic series” or overtones that are a fundamental law of acoustics. It is not, however, a real trumpet either in tone or versatility. You are really building a “PVC Bugle,” since no trumpet without valves can play all the notes of a scale. This instrument will be able to play “Taps” or “Reveille,” but not “Joy to the World.” The dimensions specified here will give you an instrument pitched in B flat.
Buy the materials. Buy 5 feet of ½=inch (inside) diameter PVC pipe, along with four 90-degree elbows. Before leaving the hardware store, you’ll want to buy a small funnel that you can insert into the PVC pipe with a good fit. If you are not using a trumpet mouthpiece for this project, a garden hose attachment can substitute. Before leaving, you’ll also want to ask the store personnel to cut the PVC pipe into these approximate lengths (cut them a little longer than specified in case you want to raise the pitch of the instrument after trying it out): two 16-inch pieces, one 11-inch piece, and two 4-inch pieces.
Assemble the trumpet. Pick up one of the 16-inch pieces and slip an elbow over one end. Connect a 4-inch piece and then another elbow that points back along the first pipe. Connect the 11-inch piece and another elbow that will point back toward the first pipe, and insert the other 4-inch piece and another elbow that points down the same direction as the first pipe. Finally, insert the second 16-inch piece and insert the funnel into its far end. On the near end of the first pipe, opposite the funnel end, you can insert your trumpet mouthpiece (it may need to be wrapped with tape to fit the ½-inch pipe) or the garden hose adapter. You’re now ready to try the instrument out. (Once it’s set, you can tape together the two longest pipes to keep the shape intact and keep the horn from falling apart.)
Try out your range and tone quality. You will only have seven or eight notes available, unless you have great high chops (the higher you go, the closer together the notes become). To play the PVC trumpet, you need to be able to buzz your lips and make sound as a player does on a regular trumpet. Even so, the tone quality won’t approach that of any real trumpet. This is partly because of the non-metallic materials, but also due to the overall shape of the pipe. A real trumpet begins to flare (expand) toward the bell sooner than our PVC pipe and funnel, giving the instrument a bigger, “fatter” tone.
Watch for air leaks and condensation. If you don’t have your component pieces securely fastened to each other, air may leak out of the middle of the instrument, creating inferior tone or incorrect pitch. Make sure that everything is connected tightly and try it again. After you play for several minutes, water will begin to collect in the tubes. This is not “spit” but condensation caused by the warm breath passing through a colder pipe. Without the water key or “spit valve” that a trumpet has, water buildup will eventually impede airflow. To get rid of the water, rotate the instrument until the water drips out of one end.
Check your pitch. Your instrument should sound pretty close to real concert B flat. You can experiment with trimming pipes shorter to raise the pitch. However, go slowly—once it’s cut, it’s cut, and there’s no lowering it again!
If you want more notes, you can double all of the dimensions of the instrument (except for the unchanged ½-inch diameter pipe) to produce a trumpet pitched a whole octave lower. This will give you many more notes and you can start to play more tunes, however the response with the double-long pipe will be “punky” and the air resistance greater. Also, some notes will sound out of tune, but this is the law of acoustics in action.