C-sharp minor is a musical key that is often associated with a somber or melancholic mood. It consists of four sharps in its key signature: F-sharp, C-sharp, G-sharp, and D-sharp. This key is frequently used in various musical genres, including classical, jazz, and contemporary music, allowing composers to express deep emotions. Many well-known pieces are written in C-sharp minor, such as Frédéric Chopin's Nocturne in C-sharp minor and Johannes Brahms's Symphony No. 1. The key's unique sound can evoke feelings of introspection and longing, making it a popular choice for composers seeking to convey complex emotional themes.