The Cmaj7 chord, or C major 7, is a four-note chord that consists of the root note C, the major third E, the perfect fifth G, and the major seventh B. This chord is commonly used in various music genres, including jazz, pop, and classical, providing a rich and warm sound. To play a Cmaj7 on the piano, you can use the notes C, E, G, and B together. On the guitar, it can be played using specific finger placements on the fretboard. The Cmaj7 chord adds depth and complexity to music, making it a favorite among musicians.