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Double Bass Harmonics
- Thread starter Andy Mopley
- Start date
There's a big article on Wikipedia.
My short resume:
When you play a tone, let's say deep A, the string vibrates on all of the modes above. Why? See here.
This means, that the sound is 'composed' from multiple frequencies of oscillation. These frequencies can be expressed mathematically, example on tone A1 (55 Hz):
mode 1 (A1) = 55*1 Hz
mode 2 (A) = 55*2 Hz
mode 3 (e) = 55*3 Hz
mode 4 (a) = 55*4 Hz
The names of the (tones) above are derived from frequencies and can be checked here.
How loud each harmonic mode is, depends on the instrument. (Trumpet has a different harmonic spectrum than piano etc.)
Your ear hears all these harmonic modes and tells the educated brain 'this is tone A1 played on double bass'. The tone of mode 1 (A1) - the lowest partial - is called fundamental.
Now. When you play harmonics, you divide the string on the node, so it cannot vibrate in the 'lower' modes. If you divide the string in, let's say, third (by softly placing the finger on the string), it cannot vibrate in mode 1 and mode 2, so the lowest frequency percepted would be 55*3 Hz = 165 Hz = e.
This is basic mathematics explained by an dilletante. For a musician, I believe the wikipedia article could be easier to understand.
There is lots of interesting information about harmonics above but I'm not sure that And's original query has been answered. Don's first response was beautifully concise and I might be able to add a little to this.
jj.83 has nicely shown the two dimensional shapes of the wave forms. The first few simple divisions of the string (1/2, 1/3/ 1/4/ 1/5) are relatively easy to produce clearly on the neck side of the 1/2 (eg octave G) without having to vary the light bow weight, speed and contact point very much. You can clearly feel the dead spots called nodes where the energy crosses over and the string does not move vertically. Call this the centre of the harmonic. As you move your finger gradually away on either side of the dead spot you feel the buzz as the string begins to vibrate until finally you can't produce the harmonic because you are now damping the vibrations. You can have a slight margin for error in finger placement and still produce clear harmonics but this margin decreases in line with the increasingly closer number of nodes and "bumps".
My suggestions are (1) the highest harmonics are best produced closer to the bridge but require careful adjustments of bow weight, speed and contact point too, and (2) the reason you may have more problems producing the same harmonics closer to the nut is the distance between the finger trying to create a node at one end and the bow working at the other end. The string will not accept the division as immediately or clearly and there is room for other sounds to interfere.
Now, my arms are not that long and high harmonics give me grief. I recall using a short stick with a little notch in the end to create a long held high harmonic in a Ravel or Debussy piece. I marked the spot on the string with a black dot.
jj.83 has nicely shown the two dimensional shapes of the wave forms. The first few simple divisions of the string (1/2, 1/3/ 1/4/ 1/5) are relatively easy to produce clearly on the neck side of the 1/2 (eg octave G) without having to vary the light bow weight, speed and contact point very much. You can clearly feel the dead spots called nodes where the energy crosses over and the string does not move vertically. Call this the centre of the harmonic. As you move your finger gradually away on either side of the dead spot you feel the buzz as the string begins to vibrate until finally you can't produce the harmonic because you are now damping the vibrations. You can have a slight margin for error in finger placement and still produce clear harmonics but this margin decreases in line with the increasingly closer number of nodes and "bumps".
My suggestions are (1) the highest harmonics are best produced closer to the bridge but require careful adjustments of bow weight, speed and contact point too, and (2) the reason you may have more problems producing the same harmonics closer to the nut is the distance between the finger trying to create a node at one end and the bow working at the other end. The string will not accept the division as immediately or clearly and there is room for other sounds to interfere.
Now, my arms are not that long and high harmonics give me grief. I recall using a short stick with a little notch in the end to create a long held high harmonic in a Ravel or Debussy piece. I marked the spot on the string with a black dot.
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