What does the term 'sostenuto' indicate in music?

The term 'sostenuto' in music instructs the performer to hold a note or a series of notes for their full value, allowing the sound to resonate and maintain its length. This technique emphasizes a sustained, legato quality, contrasting with more staccato or detached articulations. By holding notes with full value, the music can achieve a more expressive and lyrical character, often enhancing emotional delivery. Sostenuto is commonly employed in various musical contexts, especially in lyrical passages or when conveying a sense of calm and steadiness.