Etude no. 19, opus 60, GA33 by the Spanish (Catalan) composer and guitar virtuoso Fernando Sor (1778-1839), performed by Trond Undheim.
Fernando Sor was a Spanish (Catalan) Romantic performer, composer, and teacher of guitar known for being among the first to play the guitar as a classical concert instrument and for writing one of the earliest books of guitar-playing methodology, according to Encyclopedia Britannica (for a full bio, see here).
For me, Fernando Sor was my first encounter with true classical guitar music. At Middle School, I studied his 25 Etudes (introductory studies) before breakfast, which provided a calm start of my day.