What is a tone row?

A tone row is a series of notes in a fixed order, like a melody or riff but with no rhythmic values assigned to the pitches. Most commonly it contains all 12 tones of the chromatic scale just once, such as in serialised or ’12 tone’ music which requires all notes are sounded before any may be repeated.      The row can then be manipulated through inversion, retrograde and transposition to produce melody and harmony.