Diatonic harmonicas, also known as blues harps, are designed primarily for playing music in a specific key. They produce rich, expressive tones and are widely used in genres like blues, folk, rock, and country. Each hole allows for two notes—one when blowing and one when drawing—with additional pitch variations achievable through techniques like bending. While they are limited to the notes of a particular scale, skilled players can use advanced techniques to access chromatic tones, expanding the harmonica’s musical range significantly.