Chromatic harmonicas use button-controlled bars to direct the blow to specific airways. They usually play a full range of keys from a single reed plate. They are commonly used in blues, classical, jazz, and Celtic music.
Tremolo harmonicas play each note with two reeds – one playing a sharp note and the other sounding flat. This produces a distinct warbling sound with a tone midway between the two discordant notes. The most commonly used form is the Asian tremolo, which contains all possible notes.
Ten-hole harmonicas have ten reed holes, each connected to two reeds. One reed vibrates during exhale, while the other vibrates on inhale. Also called blues harps, they have a range of three octaves and can play 19 notes, although some specialized varieties have up to 42 notes. They produce notes in specific keys without the corresponding flats and sharps.
Octave harmonicas have the same reed arrangement as blues harps, except that both reeds are placed side by side on a single reed-plate. The two reeds in each hole are tuned exactly one octave apart. They are usually tuned in traditional diatonic scales, although some musicians tune them after Asian tremolos.
Horn harmonicas have large combs holding individually mounted reeds, which vibrate only on exhale. They are tuned after standard pianos or mallet instruments. The lower reed-plate holds the diatonic C scale natural notes, while the upper reed-plate holds the sharps and flats in the same scale. They come in different octave ranges. The highest pitched varieties start on the middle C, while the lowest pitches start two octaves below.
Polyphonias have a blow and draw reed, which are tuned to identical tones. They contain all 12 chromatic notes in a single line, allowing users to play notes in rapid succession without redirecting airflow. They are also capable of playing glissandos, a technique where successive notes are played seamlessly to create a sliding sound.
Bass harmonicas have two combs arranged on top of each other, joined at the ends with movable connectors. They also have two reeds in each hole, one playing a bass note and the other playing the corresponding note an octave higher. They have a very low pitch range, usually serving the function of a double bass in an orchestra.
Chord harmonicas have 48 chords consisting of major, minor, seventh, diminished, and augmented chords. In most models, each hole is connected to two reeds tuned one octave apart. Cheaper models only have one reed. They are arranged in clusters of four chords, which produce different notes on blow and draw.
ChengGong harmonicas have movable mouthpieces that slide along the body. The mouthpiece has eleven holes that redirect air to different reeds, providing up to 24 distinct chords spanning three octaves. The same note is produced on inhale and exhale, making them very similar in tuning to polyphonias and Asian tremolos.
Pitch pipes are mainly used as pitch reference for tuning other instruments, often as alternatives to tuning forks They usually produce a limited number of notes specific to the instrument being tuned. They are also used to determine pitch standards in a particular piece and to guide a cappella singers.