The Kleine Orgelsolomesse is Haydn’s last missa brevis. All these short masses share a modest orchestra.

The mass was written for the order of the Barmherzige Brüder, also called Brothers of Mercy, in Eisenstadt, Hungarian Kingdom (now Austria), whose founder and patron saint was St. John of God. Haydn lived in Eisenstadt, working for the court of Nikolaus II, Prince Esterházy. The composition was written in 1774. Because of an extensive Organ solo in the Benedictus, it is known as the Kleine Orgelmesse (Little Organ Mass), referring to the Große Orgelsolomesse (Great Organ Mass), a colloquial name for the Missa in honorem Beatissimae Virginis Mariae, Haydn's fourth mass in E-flat major. An organ solo in the Benedictus was common practice at the time.

Haydn played the organ in the first performance in the hospital chapel of the Brethren in Eisenstadt. "Kleine" (little) may refer to the composition as well as to the organ, because the instrument there was a positive with six stops without pedal.

(Adapted from Wikipedia.)