Note frequencies: understanding sound and pitch

Frequency is the physical property of a vibration, the number of vibrations per second.

Pitch is our subjective experience of those vibrations. Higher frequencies produce higher pitches and lower frequencies produce deeper pitches.

The A440 tuning standard is the reference pitch for tuning musical instruments. When you tune your piano, the note A4 is tuned to 440 Hz. Before the adoption of A440, tuning and the frequency of musical notes varied between regions and instruments, but now A440 is the standard used worldwide. 

When you play the note A4 (440 Hz), it sounds at a higher pitch than A3 (220 Hz) because its frequency is higher by one octave. 

A musical “octave” is a doubling or halving  the frequency of the previous note of the same name. This can be seen on the note frequency chart. 

Western music gets note names and pitches through ‘Twelve Tone Equal Temperament’. This standard tuning divides the octave into twelve equal divisions with a being 440Hz. This creates the twelve notes of music we see in the chromatic scale. 

A tone is a single pure sound at specific frequencies with nothing else added. Tones can be helpful for ear training, tuning, synthesis and understanding musical note frequencies and pitch.

However, when we hear a sound, such as a simple tone played on piano it is actually a collection of component frequencies which are referred to as “overtones”. These overtones exist because most vibrating objects or instruments can vibrate in more than one way at the same time. These vibrations are unique to each instrument giving instruments their own unique timbre. 

See how these overtone frequencies differ in the overtones of both a violin and piano: 

Knowing how pitch and frequency work together helps you play in tune, understand intervals between notes and even get more comfortable with variable MIDI note frequencies or digital tools like synthesizers. Harmony and melody in music is nothing more than different relationships between different frequencies and their ratios and subsequent relationships. These relationships are responsible for the musical concepts we refer to as ‘consonance’ and ‘dissonance’.