The Music Espionage

Frequencies, Fundamentals and Harmonics Explained

Understanding frequencies are a fundamental to music and music technology. It allows us to know where in the frequency spectrum different instruments lie, which in turn, affects how we record them.

Frequencies, Fundamentals and Harmonics Explained

Frequency is measured in Herts (Hz), which relates to how many times a sound wave repeats or cycles in one second. A sound wave that cycles 50 times a second is 50Hz and one that cycles 10,000 times a second is 10,000Hz or 10kHz and so on. The human ear can hear sounds from 20Hz to 20kHz and when we talk about the frequency spectrum in a musical sense, we are referring to the frequency range of human hearing – 20Hz to 20kHz.

Frequencies, Fundamentals and Harmonics Explained

At the start of recording any instrument we need to decide what microphone to use. Part of this is knowing where the instrument sits within the frequency spectrum. Take an acoustic guitar for example; as you can see on the table the acoustic guitar produces sounds between 80Hz and 15kHz so we need to ensure we use a microphone with at least this frequency range to guarantee we capture the instrument the best we can. Some microphones are specifically designed to capture certain bands of frequencies. The AKG D112 microphone is designed to capture lower frequencies and is used on kick drums and bass guitars. You wouldn’t want to use it on an instrument that produces a lot of high frequencies like cymbals.

As you can see on the graph, each instrument has two separate bars in the frequency spectrum, Fundamentals and Harmonics.

When a guitar string is plucked it does not produce one single frequency, it produces multiple frequencies, which is called a complex waveform. The lowest frequency is called the fundamental and the ones above it are called overtones. If the overtones are multiples of the fundamentals then they are harmonics.

So if a complex waveform has a fundamental frequency of 100Hz then the overtone at 200Hz is a harmonic, the next harmonic will be at 300Hz, the fourth at 400Hz and so on. Everything in between are overtones.

The different harmonics in a waveform is how we distinguish what instrument is playing and is referred to as the tonal qualities of an instrument. For example, a distorted guitar has a lot of big harmonics and hearing those harmonics is how we know we are listening to a distorted guitar.

So why is this important?

After you have captured the instrument you may want to adjust the sound using an equaliser (EQ). An EQ cuts or boosts selected frequencies, changing the sound of the instrument. For a more detailed look at EQ click here.

For example, if you have recorded a kick drum and when you play it back it is lacking some ‘boom’ you can boost the frequencies between 50Hz – 100Hz to add this colour to the track.

If you cut the fundamental frequencies the track will sound very ‘thin’ and ‘airy’, whereas if you boost the fundament frequencies the track will sound warm and smooth. If this is done to extremes the harmonics will sound ‘thin’ and ‘tinny’ and the fundamentals will sound muddy. To try this out, bring up an EQ and the master channel of a mix and cut everything below 1kHz. You’ll be left with hardly any fundamental frequencies and most of the harmonics. Then boost everything below 1kHz, notice the difference? (Be careful not to have your speakers on loud when you boost the frequencies or it may damage your speakers, ears and give your cat a heart attack.)

Example of EQ Cut below 1kHz

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Example of EQ Boost below 1kHz

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During the mixing stages of a multi-track recording, you may find that instruments don’t have a presence within the mix and it is hard for them to push through the other instruments in the recording. This may be because instruments share some frequencies together and can disrupt the sound of instruments around them.

Therefore it is a good idea to allocate certain bands of frequencies for certain instruments. This will allow space within the frequency spectrum for each instrument to be heard. One of the most common issues is with the bass guitar and kick drum. They share a lot of the same frequencies as each other and this can cause the low end of a mix to sound ‘muddy’. To tackle this issue; cut the kick at a given frequency and then boost the bass guitar in the same frequency. Then do the opposite – cut the bass at a given frequency then boost the kick drum at the same.

Frequencies, Fundamentals and Harmonics Explained
Frequencies, Fundamentals and Harmonics Explained

The images show that the kick drum has been given a boost at 70Hz and cut at 200Hz with the bass having a boost at 200Hz and a cut at 70Hz. This technique allows both instruments to be present in the mix without overlapping each other.

Hopefully this has explained the what frequencies, fundamentals and frequencies are and their importance. If you still have questions are feel like anything needs to be explained better then please contact us and we will be happy to get back to you.