If it is helpful to the original poster...my upcoming voluntaries for the next month, as a classical-pianist-at-the-organ, are:
8/10
Vaughan Williams - Prelude on "Rhosymedre" (Three Preludes Founded on Welsh Tunes)
(choral)
Couperin - Elevation (Messe pour les Couvents)
8/17
Peeters - Nostalgia, op. 59 no. 3
Bach, J.C. - Wie schön leuchet der Morgenstern (O Morning Star, how fair and bright)
Pellegrini - Canzone (detta la Serpentina)
8/24
Franck - Petit Offertoire (1885)
Raison - Trio en Passacaille, Messe du 2eme Ton
Campra - Rigadoun
8/31
Vierne - Chorale (24 Pieces in Free Style), op. 31, no. 16
Dubois - Petite pastorale Champenoise (Deux petites pieces)
Pachelbel - Toccata in d minor
9/7
Widor - III. Andante Cantabile, Organ Symphony no. 4 in f minor, op.13, no. 4
Reger - Lobe den Herren, den mächtigen König der Ehren (Praise to the Lord, the Almighty), op. 135a, no. 15
Bach, J.S. - Kommst du nun, Jesu, vom Himmel herunter (Come thou, Jesus, from heaven to earth), BWV 650
The offertories in this church need to be fairly short. I plan the voluntaries about 6-8 months in advance and try to stay a few weeks ahead in my practice. I can't speak for others, but this is what I try to do. I'll look forward to following the thread.
--KMB