The earliest form of the Blues Harp as we know it today, was the German Mundaeoline, developed in 1821. This was refined by Charles Wheatstone, known more as a scientist / electrical engineer, in 1828 and called an Aeolina. It was a thin, pocket-sized predecessor of the harmonica that measured less than 4" x 2" x 1/4". Fittingly named in honour of Aiolos, the divine Greek administrator of the four winds, the Aeolina consisted of a series of thin strips of the new metal alloy argentum (nickel silver), fitted into parallel rows of rectangular openings in an argentum plate, set into vibration "by a gentle breath alone."
The first recordings of harmonicas were made in the US in the 1920s, and mainly used by hillbilly and jug bands. Till the 1940s, it was considered more of a toy and associated with the poor. However, musicians started experimenting with techniques like tongue-blocking, hand effects and cross-harp, giving the blues harp a completely new dimension. The harp was never really a featured lead instrument in early Blues bands, being more about adding colour to a band's sound, much as backing singers enhance the lead vocals, but there were many exceptional harp players on the scene
With amplification leading to the electric blues phase in the 1950s, musicians started using the blues harp to lend variety and helped popularize the harp. Sonny Boy Williamson II, played with British blues-rock acts like the Yardbirds and Eric Clapton, and helped popularise the instrument. Little Walter developed a new technique that produced a powerful, distorted sound, becoming one of the most influential blues harp players in history. His contemporary Big Walter Horton was a favourite of songwriter and bluesman Willie Dixon, though he wasn't as popular as Little Walter because of his inconsistency and inability to lead a band.
The 1950s also produced two other great players — Howlin' Wolf, though somewhat overlooked in that role, and Jimmy Reed. In the following decade, the growing popularity of the electric guitar made the harmonica less prominent. However, artistes like Junior Wells, Paul Butterfield and James Cotton attracted fans whenever they played. Slowly, the instrument started being used in rock and folk-rock too.
In the blues, the instrument continued to be played in the 1970s, with artistes like Charlie Musselwhite, Slim Harpo, Taj Mahal, Billy F Gibbons of ZZ Top, Jerry Portnoy, Corky Siegel and Al Wilson of Canned Heat excelling in it. In the following decade, John Popper of Blues Traveler and Huey Lewis carried forward the tradition. When Little Walter joined Muddy Waters' band in Chicago and blew his harp into a microphone, he established the harp as an essential element in the urban blues sound. His insistent style and flashy fills and solos, singled him out as a brilliant player.
The Blues Harp speaks in a language that goes straight to the heart of the Blues.