What classical pieces of music were adapted for the soundtrack of G-senjou no Maou?

Question

The soundtrack of G-senjou no Maou ("The Devil on G-string") is mostly comprised of adaptations of classical music pieces. However, the tracklists I have found do not acknowledge the original source compositions, only the track names.

Which of the tracks are based on classical compositions, and what are the names of the original pieces of music?

Answer 1

I managed to get a hold of a copy of the tracklist from the OST. The soundtrack has 76 songs on it. This includes the 67 songs which appear in "Sound Mode" in the visual novel as well as several others. I have made no attempt to distinguish which of these are present in the visual novel and which were added. The OST track titles are in romaji, but the original inspiration pieces are listed in English.

A few of the pieces are original, namely Answer, Sayounara, Close Your Eyes, and Yuki no Hane Toki no Kaze. There are a few more pieces based on these, but everything else is based on some preexisting piece. A couple of the tracks would be better characterized as arrangements rather than adaptations. Valkyrie no Kikou, Wa ga Haha no Oshietamaishi Uta, and the various versions of G-Senjou no Aria fall into this category, but I have made no attempt to locate all such cases.

Disc 1

1. G-Senjou no Aria #1 [J.S. Bach - Aria on the G-String]
2. Aizou no Nare no Hate [Katakiri Rekka - Answer]
3. Katakiri Rekka – Answer
4. Uraraka [E. Grieg - Peer Gynt Suite No. 1/Morning Mood]
5. Asa no Aisatsu [J. Pachelbel - Canon in D]
6. Hiru no Asobi [L. Beethoven - Symphony No. 9/Ode to Joy]
7. Ima, Saikou ka [J. Offenbach - Orpheus in the Underworld]
8. Sora no Seki [E. Satie - First Gymnopedie]
9. Byakuya [C. Debussy - Suite Bergamesque/Clair de lune]
10. Byakuya no Mae [C. Debussy - Suite Bergamesque/Clair de lune]
11. Hansuberi [A. Khachaturian - Gayane/Sabre Dance]
12. Giwaku [F. Chopin - The Revolutionary Etude]
13. Ginen [F. Chopin - The Revolutionary Etude]
14. Gimon [F. Chopin - The Revolutionary Etude]
15. Shinjitsu [F. Mendelssohn - Violin Concerto/1st Movement]
16. Shinjitsu no Ato [F. Mendelssohn - Violin Concerto/1st Movement]
17. Houyou [G. Handel - Rinaldo/Lascia ch'io pianga]
18. Tousou [M. Mussorgsky - Pictures at an Exhibition/Promenade]
19. Tousou no Tsudzuki [M. Mussorgsky - Pictures at an Exhibition/Promenade]
20. Satori [M. Mussorgsky - Pictures at an Exhibition/Promenade]
21. Ai [L. Beethoven - Piano Sonata No. 8 Pathetique/2nd Movement]
22. Sayounara
23. Saikai no Hi [A. Dvorak - Humoresque No.7]
24. Yasuragi no Yoru [J. Brahms - Violin Concerto in D/3rd Movement]
25. Taiketsu [R. Wagner - The Valkyrie]
26. Otoko no Hanamichi [Katakiri Rekka - Answer]
27. Aishita Onna [Katakiri Rekka - Answer]
28. Michi ha Hyouga Nari [Katakiri Rekka - Answer]
29. G-Senjou no Aria #2 [J.S. Bach - Aria on the G-String]

Disc 2

1. Wa ga Haha no Oshietamaishi Uta [A. Dvorak - Songs My Mother Taught Me]
2. Hitomi wo Tojite #1 [Ayane - Close Your Eyes]
3. Ayane - Close Your Eyes
4. G-Senjou no Aria #3 [J.S. Bach - Aria on the G-String]
5. Yuki #1 [J. Newton - Amazing Grace]
6. Yuki #2 [J. Newton - Amazing Grace]
7. Yuki #3 [J. Newton - Amazing Grace]
8. Kyoukou [J. S. Bach - Toccata and Fugue in D minor]
9. Kachiku no Mure [J. S. Bach - Toccata and Fugue in D minor]
10. Shinigami [J. S. Bach - Toccata and Fugue in D minor]
11. Kage no Sasoi [F. Schubert - The Erlking]
12. Yami no Tsukai [F. Schubert - The Erlking]
13. Fushoku [C. Saint-Saens - The Carnival of the Animals/Aquarium]
14. Rakujitsu [F. Schubert - The Erlking]
15. Nigeba Nashi [L. Beethoven - Piano Sonata No. 23 Appassionata/3rd Movement]
16. The Devil [F. Schubert - The Erlking]
17. The Devil #2 [F. Schubert - The Erlking]
18. Wa ga Haha ha Kakukatarishi [J. Pachelbel - Canon in D]
19. Hitomi wo Tojite #2 [Ayane - Close Your Eyes]
20. Hitomi wo Tojite #3 [Ayane - Close Your Eyes]
21. G-Senjou no Aria #4 [J.S. Bach - Aria on the G-String]

Disc 3

1. G-Senjou no Aria #5 [J.S. Bach - Aria on the G-String]
2. Kyoushuu [L. Beethoven - Piano Sonata No. 14 Moonlight Sonata/3rd Movement]
3. Kousaku [J.S. Bach - Little Fugue in G Minor BWV 578]
4. Deochi [P. Tchaikovsky - The Nutcracker/Dance of the Sugar Plum Fairy]
5. Hitoyasumi [S. Joplin - The Entertainer]
6. Tsuikyuu [C. Saint-Saens - The Carnival of the Animals/Those With Long Ears]
7. Shundou [E. Grieg - Peer Gynt Suite No. 1/In the Hall of the Mountain King]
8. Shinsou [C. Saint-Saens - The Carnival of the Animals/Hens and Roosters]
9. Asai Gonzou [P. Tchaikovsky - Marche Slave]
10. Chijou ni Arawareshi Jigoku [C. Orff - Carmina Burana/O Fortuna]
11. Jigoku no Tsudzuki [C. Orff - Carmina Burana/O Fortuna]
12. Yamiyo Kouro [C. Orff - Carmina Burana/O Fortuna]
13. Shiyuu [L. Beethoven - Fur Elise]
14. Kecchaku [L. Beethoven - Fur Elise]
15. Valkyrie no Kikou [R. Wagner - The Valkyrie]
16. Picaresque [G. Bizet - The Girl From Arles]
17. G-Senjou no Aria #6 [J.S. Bach - Aria on the G-String]
18. Barbarian on the Groove feat. Chata - Yuki no Hane Toki no Kaze
19. Kyoufu [J. S. Bach - Toccata and Fugue in D minor]
20. Dark [F. Schubert - The Erlking]
21. Maou 3 [F. Schubert - The Erlking]
22. Ko-Fugue [J.S. Bach - Little Fugue in G Minor BWV 578]
23. Gnossienne [E. Satie - Gnossiene No.1]
24. Gekkou #1 ~3rd Movement [L. Beethoven - Piano Sonata No. 14 Moonlight Sonata/3rd Movement]
25. Gekkou #2 ~3rd Movement [L. Beethoven - Piano Sonata No. 14 Moonlight Sonata/3rd Movement]
26. G-Senjou no Aria #7 [J.S. Bach - Aria on the G-String]