Key (music)

In music, a key acts like a home for sounds. It provides a center of stability for a song or composition. A key is made of two main parts: a tonic pitch and a mode. The tonic pitch is a single note, like A or C. It is the note that a piece of music usually circles around. Most songs even choose to end on this specific pitch. The mode is a pattern of notes that creates a scale. This mode can be Major or Minor.

If no mode is mentioned, people usually assume it is Major.

Music follows specific patterns of notes called scales. A scale uses seven notes called diatonic pitches. These notes are used more often than other notes. The other notes are called chromatic pitches. To make a scale, notes follow a pattern of steps. These steps can be whole tones or semitones. A semitone is a very small musical distance. A whole tone is a larger distance. On a piano, these distances are between the keys.

You can see these steps when playing a Major scale.

Music notation helps performers know which notes to play. Musicians use a staff made of five parallel lines. A clef tells the player how to read the lines. Sometimes, notes need to be raised or lowered. We use symbols called accidentals for this. A sharp symbol (♯) raises a pitch by one semitone. A flat symbol (♭) lowers a pitch by one semitone. A key signature is a shorthand way to write these. It shows which pitches are diatonic at the start of the music.

Some instruments require special ways of writing music. Instruments like the trumpet, clarinet, and saxophone are transposing instruments. This means the music is written differently than what is played. For example, a B♭ clarinet plays a different pitch than a written C. This helps make the written music easier to read. Musicians also use numbers to talk about chords. A chord is when multiple pitches are played at once. Systems like the Nashville number system use numbers to name these chords.

There are many ways that different keys connect to each other. A diagram called the Circle of Fifths helps show these links. It shows which keys share many of the same pitches. Moving clockwise around the circle sharpens one pitch. Moving counterclockwise flattens one pitch. The circle also shows relative minors. A relative minor uses the same pitches as a Major key. However, it uses a different tonic pitch.

This helps musicians move smoothly between keys, a process called modulation.