All sounds are made up of a combination of frequencies. In music the base frequency (called the fundamental) gives gives the pitch of the sound and the other frequency components (called 'harmonics' or 'overtones') give the characteristic timbre of the note.

Frequencies are typically measured in cycles per second, using in the unit 'Hertz' (Hz).

Musical notes and frequencies are directly linked: for example the A note above middle C has a frequency of 440 Hz. Generally, musical notes will contain multiple frequencies, with one fundamental and lots of harmonics. So in fact, it is the base frequency (fundamental) of the A note which is at 440 Hz.

Altering the balance of frequencies within a sound is known as equalisation (EQ). Musicians use the EQ on their amps to shape their tone. Recording and mastering engineers apply EQ to make songs sound punchy and full.

Once the sound becomes more complex than isolated notes, it can be more useful to talk in terms of 'bands' of frequency. For example, how much sound is present in the 100Hz-200Hz band.

Sound equalizers typically have 10 or more frequency bands whose volumes can be adjusted individually to alter the overall sound.

The ability to accurately identify frequencies by ear is highly prized amongst audio engineers and is comparable skill to absolute pitch among musicians. Frequency training is an invaluable tool for troubleshooting problems when recording audio or doing live sound (for example: a 60Hz hum is often caused by electrical interference).

Regular frequency training can allow you to:

• Recognise frequencies by ear (including musical notes)
• Identify and fix common audio problems
• Get great guitar and bass tone by understanding your amplifier's EQ.
• Design sounds using FM synthesis
• Improve the sounds of your recordings by mastering equalisation
• Hear much more detail in music as your ears listen across the full frequency range

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