There are many different scales and tonalities you can play in any position because of bends (and even more for those who can overland.)
But If we consider 1st position to be our basic major scale, then here is a short introduction to the mode of each position and what it means. Note: although we do have to do a couple bends to play the complete major scale in the lower octave (namely the -2" and -3") and the 10’ bend in the top octave, I think everyone agrees that 1st position on a C harmonica naturally produced the tonality of C major.
The Major mode, also known as the Ionian mode in classical theory, is charecterized by a happy sound thanks to it’s Major 3rd, and 6th, as well as it’s major 2nd and 7th degrees. So it’s intervals are all major and perfect - 1,2,3,4,5,6,7. It’s is found in much pop, country, soul, gospel, rock, folk, reggae, and classical genres to name a few.
2nd Position is naturally the Mixolydian mode. The only difference between a Mixolydian scale and a regular major scale is the 7th degree is lowered a half-step. So you could say that the Mixolydian mode is a major scale with a minor 7th. So 1,2,3,4,5,6,b7. This sound makes it suitable for Blues, Jazz, some Reggae, as well as some Bluegrass and Fiddle tunes, just to name a few. A few famous songs in this mode are On Broadway by George Benson, Fire on the Mountain by the Grateful Dead, Low Rider by War, Crosseyed Cat by Muddy Waters, and Freddie the Freeloader by Miles Davis.
3 position is the Dorian mode, which is similar to Mixolydian, except the 3rd degree is minor instead of a major. When I learned about the Dorian mode, I thought about it as a natural minor scale with a Major 6th. So 1,2,b3,4,5,6,b7. I think the sound of this scale maybe the hippest of all the modes. Famous songs that embody this tonality are So What by Miles Davis, Riders on the Storm by the Doors, Oye Como Va by Santana, Scarborough Fair by Simon and Garfunkel, and some old fiddle tunes like Star of the County Down.
4th Position is the Natural Minor scale, also known as Aeolian, which is similar to Dorian except it’s 6th degree is a half-step lower. So 1, 2, b3, 4,5, b6, b7. This is your most common minor tonality. Most of the music in any genre that has a somber, pensive, or forbidding mood is usually in this tonality.
5th Position is the Phrygian scale, which is like Natural Minor but it also has a b2 which gives it a distinctly Spanish sound. The intervals are 1, b2, b3, 4 5, b6, b7. Because the b2 is so dissonant, that note is usually avoided by harp players (-2" and -5.) When I play 5th position I’m usually thinking in a terms of Minor Pentatonic / Blues kind of framework. This approach is very similar to playing a Major Pentatonic scale in 2nd position.
Okaaaaay. And I think that’s enough geeking out on theory for the day. LMK if you have any thoughts or questions on the subject…