A seventh chord is a type of musical chord that consists of four notes: the root, third, fifth, and seventh. It adds depth and complexity to music by introducing a seventh note, which can create tension and resolution in harmony. Seventh chords are commonly used in various genres, including jazz, blues, and classical music. There are several types of seventh chords, including major seventh, minor seventh, and dominant seventh chords. Each type has a unique sound and function within a musical context. Musicians often use seventh chords to enhance their compositions and provide richer harmonic textures.