C# minor is a musical key that consists of the notes C#, D#, E, F#, G, A, and B. It is known for its somber and melancholic sound, often used in various genres of music, including classical, jazz, and pop. The key signature of C# minor has four sharps, which are F#, C#, G#, and D#. In terms of scale structure, C# minor follows a natural minor scale pattern, which includes whole and half steps. This key is frequently associated with emotional depth and intensity, making it a popular choice for composers and songwriters. Notable works in C# minor include pieces by composers like Johann Sebastian Bach and Frédéric Chopin.