Sunday, April 15, 2012

PVC Double Reed

• 1/2'' pvc pipe (6''-2' per instrument)
• Soda bottles (for the horn bell)
• Straws of various sizes
• Craft foam sheets
• Solid wire or tape
• Acetate sheet (optional)  note this can generally be purchased in large pieces more cheaply at art supply stores rather than office supply stores.

• Drill with various bits for finger holes and straws, jumbo straws are 5/16'' (optional)
• A small saw or pvc pipe cutter
• Utility knife
• Sand paper

After many years of making Straw oboes, it struck me that there has to be a way to improve the quality of the sound and make the instrument more durable. Looking at European Oboe construction I realized it would not be a particularly easy instrument to emulate. The first attempt to make a full oboe was a long piece of 1/2'' PVC with typical straw Oboe reed inserted and a cut off 2 liter bottle as a horn bell.  The result was a loud stadium horn like noise maker which could be prompted to make all sorts of interesting timbres by biting down on the reed in different ways. This was interesting, but not what I had in mind, it was just a louder less predictable straw Oboe, not a smoother sounding one.

So instead of looking to a European Oboe, I started looking at some of the Asian double read instruments. The Tibetan Gyaling, the Indian Shehnai and the Korean Taepyeongso have more achievable form factors and their timbres are closer to a refined version of a straw oboe.  While reading about these instruments I ran into the wikipedia article on the Taepyeongso which noted that drinking straws were often used as a replacement for the traditional reeds and went on to specify how the straws were modified to make suitable reeds. The main differences between the Taepyeongso straw reed and a straw oboe was that the straw was only cut shallowly and the resulting tongues were sanded to make them thinner and more flexible to counter there short length.  Sanding each side 50-100 times (depending on the thickness of the straw) with 220 grit sand paper produced good results. This takes a lot less time than you think and really changes the timbre produced for the better.

Here are a few straw reeds we tried out next to the new Taepyeongso like instrument body.  Small straws as well as jumbo and bubble tea all worked well if they were sanded.  The Jumbo straws could be made to fit snugly into a PVC cap with a 5/16'' hole drilled in it. Bubble tea straws can be used by wrapping them with craft foam and tying it on with wire or just tape. Normal drinking straws work with the PVC cap if wrapped with a little masking tape. Wrapping enough craft foam onto a jumbo or drinking straw with tape will allow it to fit straight in the pipe without a cap. In general cutting off as little as possible from the straw by cutting the corners slightly or rounding the ends (after flattening) and then sanding both sides evenly gave us the best results.

Things to do and notice:
What we got was an instrument with a much smoother sound than a straw oboe but not as interesting as some of the traditional Asian instruments. The improvement in sound is due to the better reeds. However, this design does not have the same conical internal profile like the original instruments it is just a straight pipe so the sound produced is still inferior to the originals.  The straight pipe also effects finger hole size, small holes are enough to change pitch of the sound at the top of the instrument, but larger holes are necessary to change the pitch near the horn bell in longer instruments. The implication of this is that over sized or under sized holes are a way to get small or larger jumps in pitch beyond what their location dictates, so you could get very accurate tuning by adjusting hole size to play written music.

You can also avoid making holes altogether by adding a slide made of rolled acetate (overhead transparencies) and taping it over the pvc pipe, to create a reed trombone. Whether you use hole or not you can adjust the timbre from a smoother tone to a warbling character by squeezing the straw as it is played.  The reed is very sensitive not only does how hard you squeeze make a difference,  but where you press on it with your teeth or lips also makes a great difference in the character of the sound produced. Using different types of bottles for the the horn bell will also change the character of the sound as seen in the Tube Trumpet.


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