A musical key is a group of pitches, or notes, that form the basis of a music composition. Each key is centered around a specific note, known as the tonic, which gives the key its name. For example, the key of C major includes the notes C, D, E, F, G, A, and B. Keys can be major or minor, with major keys often sounding bright and happy, while minor keys tend to sound darker or sadder. Musical keys help musicians understand the structure of a piece and guide them in playing or composing music. They also determine the scale used in a song, influencing its mood and emotional impact. Understanding keys is essential for musicians, as it aids in improvisation, transposition, and collaboration with others.