There are numerous techniques available for playing the harmonica, including bending, overbending, and tongue blocking.
Although it is notoriously difficult and can be frustrating for beginners, one does this by relaxing and coordinating muscles in the throat, mouth, and lips.
"Bending" also creates the glissando characteristic of much blues harp and country harmonica playing.
Bends are essential for most blues and rock harmonica due to the soulful sounds the instrument can bring out.
Overbending, combined with bending, allowed players like Chris Michalek, Carlos del Junco, Otavio Castro and George Brooks to play the entire chromatic scale.
By using both bending and overbending techniques a player can play the entire chromatic scale using a diatonic harmonica.
This has allowed diatonic harmonica players to expand into areas traditionally viewed as inhospitable to the instrument such as jazz.
Although there are players who use precise overbends and bends to play the diatonic harmonica as a fully chromatic instrument, this is still very rare, not simply because the technique is very difficult, but also because it requires an extreme level of skill, as well as a perfectly setup instrument, to match the tone of an overbend to the sound of other normally played notes.
The Lip Pursing Technique is used by Paul Butterfield, Junior Wells, Sugar Blue, Stevie Wonder, Jason Ricci among many others.
With this numbering system, positions 7-11 (on a C instrument, those having keynotes F♯, C♯, G♯, D♯, A♯) are based on notes only available by bending or overblowing.
The different starting place for each position limits or extends note options for the bottom and top octaves.
The traditional harmonica for blues playing was the Hohner Marine Band, which was affordable and easily obtainable in various keys even in the rural American South, and since its reeds could be "bent" (see below) without deteriorating at a too rapid rate.
Blues harp subverts the intention of this design with what is "perhaps the most striking example in all music of a thoroughly idiomatic technique that flatly contradicts everything that the instrument was designed for" (van der Merwe [2] p66), by making the "draw" notes the primary ones, since they are more easily bent (for holes 1-6) and consist (relative to the key of the harmonica) of II, V, VII, IV, and VI.
Even among those that favor a break-in period, numerous techniques appear: some may prefer to play a new harmonica for several hours without bending notes; others prefer to play for many short periods of time with reasonable breaks in between, as recommended by acclaimed chromatic harmonica technician and player Douglas Tate.
Some diatonic players use a 12 volt car vacuum to work the reeds, which is claimed to avoid premature stress cracks.