Partain's a cappella choir piece Lux aeterna was premiered at the 1999 KMTA conference.

Gregory Partain's Requiem, which received its world premiere in Morehead 30/10/2005, was performed by a 70-voice choir and soloists Katherine Bennett and Hunter Hensley, conducted by Loren Tice.

Requiem contains:
01. Requiem et kyrie
02. Dies irae
03. Offertorium (part 1): Jesu Christe
04. Sanctus
05. Offertorium (part 2): Hostias
06. Libera me
07. Orchestral interlude: Recordare Jesu
08. Lux aeterna
09. Quaerens me
10. In paradisum

A reverent meditation on mortality, Requiem, by composer-pianist Gregory Partain, is a ten-movement work for double chorus, soloists, and orchestra, with Latin text drawn from the centuries-old mass for the dead. The piece honors tradition with musical references to Gregorian chant and modal harmonies. Rich choral sonorities and haunting dissonances provide a modern perspective.
Commissioned by the Kentucky Music Teachers Association in partnership with the Music Teachers National Association, Requiem was premiered in its original, a cappella incarnation in 2005. Says Partain, “I soon realized that I could do more to release the music’s expressive and coloristic potential and spent the next three years re-imagining Requiem to include full orchestra.”
The premier of this expanded conception was performed in Lexington, Kentucky at the Singletary Center for the Arts on November 20, 2015 by the University of Kentucky Chorale, the Lexington Singers, and local musicians, under the direction of Jefferson Johnson. Violist Margaret Karp (mvt. VII) and countertenor Joshua Steinbach (mvt. IV) were the featured soloists.
The original, a cappella version of “In paradisum” (dedicated to Danielle Martin) can be heard on YouTube at "Partain In paradisum"