CONSTRUCTION PROCESS - DAY 9

TUNING THE BARS:

With the bars cut and the holes drilled (Figure 74), we can now begin the process of tuning them. All of the bars that have been cut should be already producing a note. In fact a glockenspiel bar vibrates in many ways simultaneously, so its distinctive sound is actually many simultaneous notes happening together. The main note that gives us the identifying pitch though is the only one that we are going to actually tune for this instrument, and it is called the “fundamental”.

We can see that the vibrating bar is not moving at the nodal points - where we have drilled the holes (Figure 75). This explains why we can support the bars on the frame at these points without dampening the vibration of the note. It also means that when we are hitting the bar to test the note it will greatly help if we hit the bar in the middle, and touch the bar as little as possible, and at the nodal points. This will produce the strongest fundamental note that we are trying to tune.

If the bar dimensions are correct and all is well, you should find that the fundamental note that all the bars produce before tuning begins, is well above the target pitch. We can test this with the tuner or by ear. To lower the pitch of the bar to where we want it to be, we must remove some of the steel from the area of the bar where the antinode is. That means right in the middle of the bar or as close to it as we can get. I have found that the fastest and easiest way to is to use the drill press with a medium sized drill bit (Figure 76). You don’t want to drill all the way through the bars of course, but on the underside of the bars you start drilling a number of holes all closely grouped around the middle of the bar (Figure 77). Some bars will need a lot more drilling than others to reach target pitch, so test each bar thoroughly and often as you tune it.

The idea is to test the bar pitch, then drill away a little more from the middle of the bar, then test the bar pitch again. You will find that as the pitch gets lower, the lowering effect also accelerates which means you usually don’t need to drill as much as you estimate you should. It pays to be cautious, if you accidentally drill too much, it is difficult to raise the bar’s pitch again a significant amount so drill gradually.