In Blues playing, it is common to add notes from outside the major key, and to alter some of the notes to make the overall sound more "bluesy". The most common alterations are the flattened third (b3), the flattened fifth (b5) and the flattened seventh (b7). These are called Blue notes, or Blues notes. The first blue note we will examine is the b3 which is Ebin the key of C. listen to how effective it sounds when alternated with the natural 3rd degree (E).
This example uses the flattened fifth (Gb) and the flattened seventh (Bb) along with the flattened 3rd (Eb). Notice how effective blue notes sound when combined with harmony notes in bars 3 and 4. Once you can play this example, try improvising with chord tones and blue notes.