Legend has it that the harmonica was invented in the 1820s by a young German man called Christian Friedrich Ludwig Buschmann. His so-called “Aura” was a free-reed instrument consisting of a series of steel reeds arranged together horizontally in small channels. Early designs were widely imitated, leading to many modifications and advancements: around 1826, a Bohemian instrument maker named Richter created an instrument remarkably similar to modern diatonic harmonicas. He developed a variation that consisted of ten holes and twenty reeds, with separate blow and draw reed plates mounted on either side of a wooden comb. Most importantly, the way that the notes were arranged was exactly the same as it is today. Richter’s tuning became the standard configuration of what Europeans referred to as the ‘Mundharmonika’ or mouth organ.
Richter (being German) was a very logical and organized musician. He arranged the notes the way he did for a very specific purpose: he planned to make it easy to play European folk and classical music on the harmonica. The major and minor scale are the musical alphabets of most European folk and classical music, so Richter arranged the notes of the harmonica so that is would be easy to play major and minor scale. For example, the C major and A minor scale can be played easily on ten-hole harmonica in the key of C. However, in order to achieve his intended layout, he was forced to leave certain notes out of the harmonica; so many notes, in fact, that players must learn to bend existing notes to supply the missing ones.
You can probably tell, from the above diagram, that almost all the notes needed in order to play three complete octaves of the C major scale and several octaves of the A minor scale, are present on the C diatonic harmonica. Plus, the layout is such that if you blow into any three consecutive holes you end up playing the C major chord. Not only that, but by drawing on holes 1, 2 and 3 you produce the G major chord (the second inversion, see the next section for details), and by drawing on holes 4, 5 and 6 you produce the D minor chord. In doing this, it was Richter’s intention to create as much versatility as possible in his small, metallic instrument.
The diatonic harmonica came to America during the American Civil War, after which many of the former slaves searched for an inexpensive and portable instrument to help them let out their rich musical heritage. But the kind of music that African-Americans played was very different to the European folk and classical music for which the diatonic harmonica had been designed: their music was a very rhythmic and vocal sort with strong emotion and runs of improvization. Plus, the notes they prefered to sing were in between the major and minor scales: notes that could be easily sung but were impossible to play on the piano without special tuning. You could almost say that they were in the cracks between the keys. The notes that were sung also tended to be warbled and slurred, which was definitely impossible on the piano. What was needed was an instrument that could be controlled by the same muscles that controlled the voice.
After many years of trial and error, a new scale evolved: it had only seven notes and was a fusion of both the major and minor scales. It was lovingly christened the blues scale. This new scale, and a new chord structure called the twelve bar blues (more on that in a later section), merged to form a brand new musical style that combined the emotion of traditional European music, the rustic tones and rhythms of African music, and the creativity of American music: the Blues.