In Western music, most instruments are designed to play twelve notes in an octave. These notes are represented as A, A#/Bb, B, C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, and G#/Ab, where the # indicates the note is played higher than normal, and the b indicates it is played lower. For example, A# would be the same note as Bb, as the note falls between A and B in a 12-note chromatic scale. A chromatic scale can start at any note, but will follow the same pattern.
Compare to diatonic scale.