---
title: Notes & Pitch
category: Fundamentals
slug: notes-and-pitch
related: [intervals, scales, keys-and-key-signatures]
url: https://fourthshub.com/docs/notes-and-pitch
---

# Notes & Pitch

## The 12 Notes

Western music divides the octave into **12 equally spaced pitches**, called the **chromatic scale**. Starting from C:

**C - C#/Db - D - D#/Eb - E - F - F#/Gb - G - G#/Ab - A - A#/Bb - B**

Each adjacent pair is separated by a **half step** (semitone), the smallest interval in standard Western music. Two half steps make a **whole step** (whole tone).

## Enharmonic Equivalents

Most notes have two names. C# and Db are the *same pitch* spelled differently. Which name you use depends on the key and harmonic context. In the key of D major, you write F# (the third degree); in the key of Gb major, the same pitch is Gb (the root).

## Octaves and Frequency

When you double a frequency, you get the same pitch class one **octave** higher. The note A4 vibrates at 440 Hz (the standard tuning reference). A5 is 880 Hz, A3 is 220 Hz. Every octave is a 2:1 frequency ratio.

## Pitch Class

A **pitch class** groups together all octave-equivalent versions of a note. "C" as a pitch class includes C1, C2, C3, and every other C. There are exactly 12 pitch classes, and they repeat endlessly up and down the frequency spectrum.

## MIDI and Scientific Pitch Notation

In scientific pitch notation, middle C is **C4** (MIDI note 60). Each octave number increments at C, so B3 is immediately below C4. This system removes ambiguity when discussing specific pitches across instruments.

## On the Guitar

In standard tuning, the open strings span almost four octaves. In fourths tuning (E-A-D-G-C-F), the open strings cover a slightly wider range and are spaced with perfect geometric regularity, which means the same interval shape works identically on every pair of adjacent strings.