This song by Styx is in D.
Part 5 and 6 are the interlude.
These are the “cheat” chords I played…
Part 1a: Bm7 - Em7 - A11 - A
Part 1b: same as Part 1a
Part 2a: Bm7 - GM7 - A
Part 2b: Bm7 - A - A11 - A
Part 3: D - Em7 - A11 - D - A11
Part 4a: D - DM7 - G/D - Bm7 - A - Bm7 - A
Part 4b: same as Part 4a
Part 4c: GM7
Part 5: D - Em7 - D - A11
Part 6a: Bb - C/Bb - Bb - C/Bb - D/A - A11 - D/A - A11
Part 6b: Bb - C/Bb - Bb - C/Bb - A11 - A - A11 - A
