In The Well-Tempered Clavier, these pieces are paired with fugues.
Paul Hindemith's Ludus Tonalis opens with a piece of this type. The tempo marking "Allegro ritmato e deciso" is appended to the first and third of three works of this kind by George Gershwin, which Jascha Heifetz transcribed for the violin. A J.S. Bach piece of this type is the basis for Charles Gounod's "Ave Maria". One of these pieces nicknamed "The Bells of Moscow" is a work in (*) C-sharp minor by Rachmaninoff. Chopin wrote 24 pieces in this genre, arranged according to the circle of fifths, the most famous of which is the one in D-flat nicknamed "Raindrop". In The Well-Tempered Clavier, these pieces are paired with fugues. For 10 points, name these pieces, whose name suggests their function as introductions.
Paul Hindemith's Ludus Tonalis opens with a piece of this type.
preludes [or vorspiel or praeludium]