The harmonica is based on an ancient instrument, the sheng which is one of the oldest Chinese musical instruments. The instrument existed as far back as 3,000 years ago. Up to six notes can be played simultaneously, therefore, it is commonly called as the "Chinese mouth organ". Sheng is also the first musical instrument in the world utilizing a "coupled acoustical system," between an air column and a free reed. Sheng consists of 13-17 bamboo pipes with different lengths that are mounted together onto a base. The base is traditionally a gourd-shaped, wooden wind-chest. Each bamboo pipe has a free reed made of brass.

The origins of the harmonica are obscure, but it seems that the harmonica, as we know it today, appeared first in Germany, in an amazing tale which begins in the year 1821. It was then that sixteen-year-old Christian Friedrich Buschmann registered the first European patents for his new musical invention. His so-called "aura" was a free-reed instrument consisting of a series of steel reeds arranged together horizontally in small channels. An awkward design, approximately 4 inches wide and tall, it offered only blow notes arranged chromatically. Buschmann described his new instrument to his brother as "a new instrument that is truly remarkable. In its entirety it measures but four inches in length...but gives me twenty-one notes, and all the pianissimos and crescendos one could want without a keyboard, harmonies of six tones, and the ability to hold a note as long as one would wish to. Initial designs by Buschmann were widely imitated, leading to many modifications and advancements.

The next version of the modern harmonica came from a Bohemian immigrant Anton Richter. He created a 10-hole, diatonic harmonica called the "Vamper" with two stacked reed plates that would produce a consistent tone when blowing or drawing air over the reeds. Its size, approximate 4 inches wide but only 1 inch tall, made it an immediate improvement over its predecessors. Still, the modern harmonica was more a curiosity than a respected instrument. . Richter's tuning, utilizing a diatonic scale, became the standard configuration of what Europeans referred to as the Mundharmonika or mouth organ. In 1825 Fr. Hotz began producing mouth organs in his factory in Knittlingen, Germany. Another German, Christian Messner, acquired some of Christian Buschmann's auras. He set up shop in his clock making firm in Trossingen in 1827 and began manufacturing instruments that were similar to Buschmann's 'aura.' Messner called these instruments mundaeolines. During the year 1829, J. W. Glier began manufacturing mouth organs at his factory in Klingenthal, Germany. In 1855 the German, Christian Weiss, started producing mouth organs. Finally in 1857 a firm in Trossingen Germany began mass producing harmonicas for the public.

At the head of this company was the famous Matthias Hohner who changed  the history of the harmonica dramatically, when the German clock maker, turned to manufacturing harmonicas full-time. With the help of his family and a hired workman, he was able to produce 650 instruments that year. Soon after, he added local workers and developed mass production techniques. Young Hohner was an outstanding businessman and showed his marketing savvy by developing ornate cover plates bearing the producer's name.

He introduced the harmonica to North America in 1862, a move which would propel the Hohner company to its status as the world leader in harmonicas. He sent a small supply of his harmonicas to his cousins, who had emigrated to America a few years earlier, with the intent of establishing a market for his instruments. The tone and beauty of these simple instruments quickly won over many Americans, despite the looks of puzzlement these "immigrant salesmen" were likely given as they introduced their wares. Its portable size, quality construction, and superb tone made harmonicas a quick addition to the American landscape. Hohner almost singe-handedly established the harmonica, in America, as a musical lexicon.

Hohner  actually was more an entrepreneur than an inventor, as evidenced by his clever exploitation of the prestige of well-known musical figures to enhance the appeal of his instruments. The Marine Band model, which became the most popular harmonica of all time, was named after the famous band led by American bandmaster John Philip Sousa. Sousa himself was persuaded to endorse the Hohner harmonica in a statement printed on the instrument box and reproduced in advertisements across the country. "This instrument is a foundation for a musical career," Sousa said, "and many boys and girls who are now learning music on the harmonica will step into the great symphony orchestras and bands of our country some day." By 1887, Hohner was producing more than one million harmonicas annually.

When Hohner died in 1902, his name had become virtually synonymous with "harmonica." From an original staff of one in 1857, the Hohner company grew to 3,000 employees in 1913, who produced 10 million instruments that year. By the 1920s, sales had grown to 25 million instruments a year with more than 5,000 skilled workman. M. Hohner, and his family donated the land, and built the City Hall ( which still stands today) for Trossingen in the early 1900's. It is situated straight down the street at the end of the factory, and faces Hohner's own home.

The chromatic harmonica, introduced in the 1920's and championed in the 1930's by the virtuoso player Larry Adler , was the single most significant improvement in the evolution of the instrument. There are two main types of chromatics: The solo tuned harmonicas, and accompaniment harmonicas. The first type is used for playing solos, and participating in ensemble groups. The solo tuned chromatics are able to produce half tones (sharps and flats) with the use of a slide button (located at one end of the instrument). Chromatic harmonicas have ranges that are: 2, 2 1/2, 3, and 4 chromatic octaves. The second type of chromatic harmonica is the bass harmonica, this instrument provides the fundamental bass tones used for orchestral accompaniment. 

Today, Hohner produces over 90 different models of harmonica, with a variety of styles and tunings which allows the player freedom of expression in all forms of music, from Classical and Jazz to Blues, Country and Rock, to the indigenous music of people worldwide.