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Notes on some things not to do

Reed instruments

As mentioned in the clarinet discussion, reed instruments need a lot of holes to get a full Western scale in multiple octaves.  Wooden reeds provide these holes using keys that enable one finger to close multiple holes.  You could do the same for gourd instruments, but I haven't.  Or you could use a scale with fewer notes or a single octave.

The reason reeds need more holes than flutes is this:  A flute with all its holes covered will resonate at is lowest pitch, the pitch an octave above (2x the frequency), the pitch 2 octaves above (4x the frequency), etc.  A reed with all its holes covered will resonate at is lowest pitch, the pitch one and a half octaves above (3x the frequency), the pitch two and a third octaves above (5x the frequency), etc.  The flute is like a jump rope tied at both ends and pumped in between, while a reed is like a jump rope tied at one and pumped at the other.

The flute is like a jump rope tied at both ends and pumped in between.  With all its holes covered, it will resonate at is lowest pitch, the pitch an octave above (2x the frequency), the pitch 2 octaves above (4x the frequency), etc.

The reed is like a jump rope tied at one and pumped at the other.

With all its holes covered, it will resonate at is lowest pitch, the pitch one and a half octaves above (3x the frequency), the pitch two and a third octaves above (5x the frequency), etc.

   

Cedar marimba bars

Cedar is cheap and easy to work with, and it rings well.  This marimba is made with 3" x 7/8" cedar--about $20 worth.  I tuned it by carefully cutting each bar to the desired length. 

Normally, marimba bars are tuned by removing material from an arch in the underside.  Hardwood bars will drop over an octave in pitch when you make an arch half the thickness of the bar.  But these bars only dropped 3 to 4 half-steps before becoming too thin. 

For bars of this pitch, it would have been nice to be able to tune the overtones, but I couldn't do that with this wood.  When I added resonators, that helped.  So keep all this in mind if you think about making a marimba from soft wood.

Grounding bar kalimba

The tongues of this kalimba are held by an electrical part called a grounding bar.  It was extremely easy to make and I was happy with the sound.  The only drawback was the limited range--7 notes.

So I tried to scale up with a bigger gourd and bigger grounding bar but ran into a limitation that prevented me from using wider tongues, which I needed to exploit the greater volume of this gourd.  The wide tongues did not sit flat because of the round bottom of the hole through which they pass.  The edges of the tongue encountered the sides of the hole, and I could not squeeze them tightly enough to get good resonance.  I'm no longer enchanted with the grounding bar and an alternative to standard kalimba hardware.

Gourd tongue drum

The tongues on this drum don't ring well, because the gourd lacks the mass necessary to stabilize the face.  The base of the tongue (where it connects to the rest of the face) needs to be held still in order for the body of the tongue to vibrate.  If the base vibrates, energy is lost into moving the face, and the sound thunky.  Wooden tongue drums consist of a very thick-walled (~1") box with the face firmly attached.  Because gourds just don't provide that kind of mass, I now consider tongue drums to be poor candidates for gourd instruments.

 

Friction pegs in gourds

 

This dulcimer initially had friction pegs and fine tuners, life a violin.  But over time, the holes in which the pegs sat grew, because the gourd wall compressed.  Eventually, the tapered peg topped out against the gourd, and I replaced the friction pegs with machine tuners.