The previous tutorial on making branch flutes explained how to carve the two main chambers of the flute. Now, it is time to create the heart of the instrument – the sound mechanism. The sound mechanism is made of a nest, in which there are two holes and a shallow channel between them. To make the sound mechanism, a craft knife, a small chisel and some sanding paper are required.
The sound mechanism is the heart of the instrument. The quality of this element directly influences the quality of the sound and tuning. That is why you must take great care when making this part of the flute. Be patient and proceed in small steps. It’s better to be slow and make a good sound mechanism, than being too fast and break the instrument.
Let’s start with theory
Take a look below to see how the sound mechanism looks like on the outside.
Your Native American Flute makes the sound when the air, blow into the blow hole, travels into the air channel (the windway), where it is compressed, and then it hits the splitting edge. This causes the air to resonate in the sound chamber, thus the sound is made.
The splitting edge is located in the True Sound Hole. The True Sound Hole, TSH in short, can be round, but the best results in sound quality comes from square or rectangle-shape hole.
The TSH must not be too large, nor too small – otherwise, the sound it produces won’t be of best quality. Also, the longer the flute, the bigger the sound hole must be. That is why large flutes have quite large TSH, and small flutes have a small TSH.
The sound produced by the flute depends on the quality of the True Sound Hole. First, the surface of the nest (sound mechanism) must be very flat, so that a piece of wood called “block” will fit it perfectly flat, and the air won’t escape from the air channel any other way than through the sound hole.
Next, the splitting edge must have proper angles – the bottom cut (bottom chamfer, ramp) is usually made with 45 degrees. When the air channel is placed within the block itself, the splitting edge has no upper chamfer cut. But then the channel is placed within the flute’s body, the true sound hole is usually sanded down on the top, too, to make a small chamfer cut down.
In this tutorial, I will explain how to make an air channel (the windway) within the flute’s body.
Leveling the Nest
First, let’s make a flat surface on the top of the branch. So take half of your branch, carved in the previous tutorial, mount it in the vice with the outer side facing up, and get to work.
When you gain more experience, you will be able to glue a flute first, and then make the sound mechanism later. This comes in handy when you drill the bore instead of carving it, or when you make flutes out of a single piece of bamboo. But as long as you’re a beginner, you should make the sound mechanism first, and then glue the pieces back together later. It’s the best way to learn.
Take a knife and cut off some material from the branch, like on the photo below.
Then, take a piece of square wood, wrap it in sanding paper, and sand down the branch’s flat surface. The best way to do so is to move your sanding “block” in one direction. Let’s say one end of your branch is the A end, and the other is the B end. So sand down the nest by moving your block constantly from end A to B, or B to A – but NEVER from A to B then from B to end.
When you sand down only in one direction, you have greater chance of creating a flat surface – but when you sand down in both directions, you may actually create a concave or convex surface ;).
You may also use a wide, flat chisel to cut a flat surface on the branch. Remember – the surface of the nest must be flat, so that the block fits it perfectly, and air won’t be able to escape from the air channel.
With flat surface ready, you can mark the borders of the inner wall that separates the air and sound chambers. First, you can use your eyes and a pencil – look at the bottom of the wooden piece and draw a line on the outside of the branch where the inner wall goes. Or, you can use a small drill bit. Drill very small guiding holes on both sides of the inner wall – like on the photo below:
You’re drilling from the inside of the chambers. Make sure to either put a lot of tape on the outside, or support the wood by placing the flat surface face-to-face with flat piece of wood. This way, you make sure you won’t rip of pieces of wood when you drill.
Such guiding holes will help you see the borders of the inner wall on the outside.
Either way, mark the borders of the inner wall on the flat surface of your nest, using a pencil.
Now, we need to do some measurments. Take a ruler and a pencil and copy the following image onto the flat nest surface.
The left dark area is the hole leading to the front air chamber. Next to it, on the right, is the ramp leading from the air channel down into the air chamber. The flat surface of the air channel should be 1/2 of the sound chamber’s bore diameter.
The right dark area is the true sound hole.
The holes and air channel should be anywhere between 6 to 10 mm wide. Flutes with bore diameter less than 16 mm should have the holes and air channel about 6 mm wide, while flutes larger than 16 mm in bore diameter should have the holes and air channel about 8 mm wide.
The length of the sound hole should be 5-8 mm long. Small flutes stick to 5 mm, large flutes stick to 8 mm.
If the sound hole is too small, the flute will have a tendency to overblow. If the sound hole is too large, the flute will sound airy.
After marking all the lines, you should have something like this on your branch:
The goal is to make this:
Let’s get to work. Usually, I recommend making the holes first, then making the channel between them later. You need a small, flat chisel. It should be wide enough to fit the marked size of the air channel. So, if your air channel and holes are 8 mm wide, your flat chisel should be 8 mm wide. Of course, you can work with smaller chisel, too.
Tip of the day: do not make cuts of the hole too close to the borders of the inner wall. If you made a mistake when taking measures and marking the inner wall, your chiseling may rip of pieces of the wood from that wall. And if you lose that piece, the wall may not be tight enough for the flute to work.
Important thing – if you never made a square holes in wood, practice it few times in a separate piece of wood and learn first. You really want to learn first :). Usually, first you use a chisel to make a hole, then you make small diamond files to perfect the hole by sanding it down.
First, either use a craft knife or chisel to cut the borders of the hole. Cutting the borders will make sure you won’t rip off too much wood from places where it’s not recommended :).
When four sides of the hole are cut, so you can stick the chisel in the middle of the hole, and cut off the material from the middle of the hole to its side – then repeat the process on the other side.
Below, take a look at simple guide to cutting square holes with chisel:
Piece by piece, the work should progress.
This is a slow process. Cut the borders, then cut off the surface of the hole. Cut the borders deeper, and repeat the process until you make a hole in the branch.
If you’re not comfortable with the chisel, you can drill a hole with a drill and drill bit, then use small diamond chisel and a lot of patience to sand the rectangle hole.
Use this knowledge to create two holes – one leading to the air chamber, and another leading to the sound chamber.
If you do not have a chisel or a square diamond files, you can drill a sound hole at an angle of 45 degrees and use rounded sanding paper to sand down the hole to create a sharp edge – the flute should work, as well.
Before we move on, take a look on the picture below. It’s a side cut presenting the sound mechanism.
Cutting the Windway
Now, let’s make a windway between the two holes. The windway, also known as air channel, is a shallow flat surface between the holes – but there’s also a ramp (cut at an angle) leading up from the air chamber to the air channel. As the air travels into the air channel, it is compressed and results in better quality of the sound.
To cut the air channel, first cut the side borders of the channel, so you won’t rip off unnecessary wood material from the sides. Then, use a chisel to cut a shallow channel – about 0,7 mm deep. 0,5 mm may be too shallow, and 1 mm may be too deep. Air channel that is to shallow won’t produce a strong and steady sound, while air channel that is too deep may result in the flute being too airy in sound. Basically, it’s better to create a smaller channel first, because you can always make it deeper. It’s easier than trying to make it smaller later :).
Let’s make the ramps
By now you should have two rectangle holes and a channel between them. It’s time to create three ramps – the first one leads from the air chamber to the air channel. The second one will be on the inside of the air chamber to enlarge the hole. The third one will be on the inside of the sound chamber, and it will create a splitting edge of the True Sound Hole.
Let’s start with the first ramp. It’s the one leading from the air chamber into the air channel.
Use a craft knife to cut the borders at an angle, and then use a chisel to cut down the ramp from the top into the air chamber. It’s quite simple.
Now flip the branch, and create another ramp on the same hole, this time on the opposite side.That means: make a ramp on the inside of the air chamber, leading from the air chamber up to the hole’s exit. This ramp is located on the opposite side of the inner wall that separates the chambers.
Finally, let’s make the third ramp, one on the bottom of the true sound hole. This is very important element of the sound mechanism, so be careful.
This ramp should be cut at an angle of 45 degrees. Small variations of the angle should not be a problem, but try to stick to these 45 degrees. You can use a chisel to cut the ramp, or just diamond files to sand it down. If you use a chisel, don’t make the entire ramp with it – cut out as much material as possible, but make the finishing touches with the diamond files.
Now, let’s use diamond files and sanding paper to sand the sound mechanism. Use diamond files to sand the ramps, their flat surfaces, sides etc. Make sure that the drop from the air channel into the sound hole is at 90 degrees angle.
Sand down all the sides of the holes, and fold a sanding paper to sand down the flat surface of the air channel.
On the photo above, you can see examples of finished sound mechanisms. Quite often, the top surface of the splitting edge is sanded down, too – but we won’t do this right now – this should be done later, when the flute is glued and ready for tuning. Actually, you don’t have to make the true sound hole and splitting edge perfect just yet – just make sure it looks right. We’ll do the rest later.
This completes the process of making the sound mechanism for your Native American Flute. The next tutorial will cover the final inside sanding. Then , we will glue the flute back together, and perform first sound tests.
If you have any questions, please ask them in the comments below.