Richter-tuned harmonica

The Richter-tuned harmonica, 10-hole harmonica (in Asia) or blues harp (in America), is the most widely known type of harmonica. It is a variety of diatonic harmonica, with ten holes which offer the player 19 notes (10 holes times a draw and a blow for each hole minus one repeated note) in a three-octave range.

The standard diatonic harmonica is designed to enable playing chords and melody in a single key. Because of this design, playing in different keys requires the player to have a separate instrument for each key they play in. Harps labeled G, A♭, A, B♭ or B start (on hole 1 blow) below middle C, while those labeled D♭ through F♯ start above middle C (C4). Here is the layout for a standard diatonic harmonica, labeled C, starting on middle C (C4):