Major Diatonic The Major Diatonic harmonica is the most commonly used tuning for playing BLUES ROCK COUNTRY FOLK FOLK ROCK & JAZZ. This is the traditional blues and rock harmonica tuning. Lee Oskar’s professional line of harmonicas is known for superior quality of materials construction design and sound second to none. These are the best harmonicas in the world and that’s not just our opinion. All over the world professional players prefer Lee Oskar Harps over any other brand.