Music theory can be a complex and confusing topic for many people. However, understanding the basics of music theory is essential for any aspiring musician or songwriter. One concept that often causes confusion is the term “A” in music theory.

What is A in Music Theory?

In music theory, the term “A” refers to the note A on the musical scale. The note A is used as a reference point for tuning musical instruments and is also used as a starting point for creating musical compositions.

Standard Tuning

When referring to tuning a guitar or other stringed instrument, the note A is typically used as a reference point. Standard tuning for a guitar starts with the sixth string tuned to E, then progresses to A, D, G, B, and finally high E. This means that when you tune your guitar or another stringed instrument, you’ll start by tuning the second string (A) to match the pitch of an external reference tone at 440 Hz.


The pitch of A used as a reference in standard tuning is known as A440. This means that the frequency of this note is 440 Hz. This frequency was chosen as the standard for tuning because it’s easily divisible by many other frequencies used in music composition.

The Importance of A in Music Theory

As mentioned earlier, the note A serves an essential role in music theory. It’s used not only for tuning purposes but also as a reference point when creating musical compositions and arrangements.

Key Signatures

In addition to standard tuning, A also plays an important role in key signatures. Key signatures determine which notes are sharp or flat throughout a piece of music.

For example, if a piece of music has two sharps in its key signature (D major), one of those sharps will be on F#, and the other will be on C#. However, the note A is always natural in the key of D major.


A is also a crucial note in chords. Many chords, such as A minor, A major, and A diminished, use the note A as their root. Understanding how to build and play different chords using A as a starting point is essential for any aspiring musician.


In summary, the term “A” in music theory refers to the note A on the musical scale. It serves an essential role in tuning instruments, key signatures, and building chords. Understanding this concept is crucial for any musician or songwriter looking to create compelling musical compositions.