Hexachordum Apollinis is a collection of keyboard music by Johann Pachelbel, published in 1699. It comprises six arias with variations, on original themes, and is generally regarded as one of the pinnacles of Pachelbel's oeuvre.
Pachelbel wrote a short preface in which he dedicated the collection to Dieterich Buxtehude and Ferdinand Tobias Richter and expresses a hope that his eldest son Wilhelm Hieronymus might study with one of them (it is unknown whether this hope was realized). Pachelbel also confesses that "something weightier and more unusual" than this work should have been written for the occasion; apparently feeling that this is not his best work.
Pachelbel alludes to the "friendly nature" of Buxtehude and Richter, which might indicate that he knew one of them or both, perhaps through correspondence.
Pachelbel's themes are simple song-like pieces in two sections: four bars in the first section and four or eight in the second. Both sections are repeated.
The variations conform to the same concept: most are in common time (except for Aria Sebaldina, in which all variations are in triple time, like the theme) and explore various constant harmony and melodic outline models. Although the frontispiece indicates that the work is intended for either organ or harpsichord, much of the music is better suited for the latter,