Guitar is not an everyday member of classical music family. It's soft, so it may get lost with the orchestral sounds. Here is a bang-on reason:
Guitars are often solo instruments, but before the days of amplification, they wouldn't project over full sections of strings or winds. [source]Yet, we will see that it sounds magnificent with the orchestra. Today, we listen to a guitar concerto, and probably the most popular one.
Wikipedia tells us straight
Rodrigo's music is among the most popular music of the 20th century. In particular, his Concierto de Aranjuez is considered one of the pinnacles of Spanish music and of the guitar concerto repertoire.
