B-flat minor is a musical key that consists of the notes B♭, C, D♭, E♭, F, G♭, and A♭. It is known for its dark and somber sound, often used in classical and contemporary music to evoke deep emotions. The key signature of B-flat minor has five flats, making it distinct from other minor keys. Many composers, including Johannes Brahms and Frédéric Chopin, have utilized B-flat minor in their works. The key is often associated with themes of melancholy and introspection, making it a popular choice for slow movements and lyrical passages in various musical genres.