Frequency is the basic component of all musical instruments. For the bass guitar, the frequency is the rate at which the strings played are vibrating, which creates sound.
These sounds are really pressured waves in our atmosphere, which we hear, and are part of the audible Frequency Spectrum. For a trumpet, it is the rate at which the player’s lips are buzzing at the mouthpiece.
For example, the Low E string on the bass is vibrating at 41 cycles per second or Hertz. Hertz is the standard unit of frequency and is often abbreviated as Hz. 1000 Hertz is often referred to as 1 Kilo Hertz or 1KHz. Thus, 2.5KHz is also 2500 Hertz. The A that an orchestra tunes too before a performance is 440 hertz.
When the frequency is doubled, the frequency has the same note value but is an octave higher in pitch. Thus, 440 hertz is the note A for violins to tune their instruments to before a performance (specifically the A string), but 880 hertz is an A also, but an octave higher (This is the first A on the E string for a violin).
There are twice as many vibrations per second for the 880Hz A as there are for the 440Hz A. Conversely when the frequency is cut in half, the note being played is an octave lower. This means that 220Hz is also an A (This is the first A on the G string of a violin).
110Hz is two octaves below the 440Hz A string for violins. This 110Hz is the A on the G string of a bass guitar or bass violin. The A string on the Bass is 55Hz. One octave below that is the low A on the piano at 27.5Hz. The Low B string on a 5 or 6-string bass is about 31Hz.
However, it should be remembered, that whenever you play a note, you are rarely playing one frequency. Most of the time, when a note is played, there are overtones that accompany the sound.
If you were to take snapshots of the string being played you would find that the string is vibrating with a mix of patterns. This is partly a factor of where the string is plucked along the length of the string.
As move your plucking hand to the middle of the string length, for any given note, there will be fewer overtones being played, and more of a pure fundamental note being played.
As move your plucking hand toward the bridge of the instrument, the tone will become more nasal sounding, and it will have more overtones and less fundamental tones. Thus, in the normal course of the playing, your bass will be putting out several tones at once.
For example, if you were to simply play the A string on the bass, there would be several overtones that usually accompany the sound. The fundamental note is 55Hz. There would also be an overtone at 110Hz, at 220Hz, and even for a short time some at 440Hz.
These are all harmonic overtones. There are other overtones which would be octaves of what is called the fifth. For note A, the fifth would be noted E. Thus, some of the sounds of note A have some traces, of E at 82Hz, and 164Hz, and 328Hz.
Sometimes, the string produces overtones that are not consistent with the fundamental note. These are sometimes called false harmonics. This is usually the result of the string being too short for the note being played.
This is why on expensive pianos the soundboard is nine feet long for the lower strings, and these notes sound much better because the strings are long enough for the lower frequencies to develop properly.
On cheaper pianos with shorter soundboards, the lower notes have noticeable false overtones. The same thing happens on bass guitars. This is why many basses come in 35, 36, and 37-inch long string scales, especially when the bass has a low B string.
One of the common questions placed online about the bass is what is the frequency of certain notes on the bass.
Below is a table that contains the frequency for the notes on the bass. I am including six-string basses here, but only the first four frets (or half steps) on the neck. Four-string basses are in the Blue text below.
Remember that this table only gives you the fundamental frequency, which is the predominant frequency for the note. In reality, there are almost always harmonics which always accompany the note and give color and texture to the sound.