Seventh Son has always struck me as an album with a lot of key changes, and using keys in a creative way, even if the main key, a lot of times, is still E minor. For me these key changes is what gives Seventh Son such an epic feel, something that they havent done in the same way neither before or after.
Moonchild - E minor, B Frygian bridge, Am solo.
Infinite Dreams - Mostly E minor, 1.42 shifts to Gm and back to Em, back and forth, bridge 4.22 in F#m, outro again shifts between Em and Gm
Can I Play With Madness - D mixolydian, B minor chorus, bridge starts in Em, shifts to Gm, same with solo.
The Evil That Men Do - Probably the safest one key-wise, mostly E minor, solo in F#m
Seventh Son Of A Seventh Son - First half in Em, soft bridge shifts between the key of Em and Cm, Solo in F# Frygian, lick in F#m, next solo in C# Frygian, F# Frygian going to F#m for the outro
The Prophecy - All over the place. Start in Am. Verse in Dm, 2nd half in Em, then back to Am, then to Ebm for the chorus. We go to Em for the instrumental, which then halfway changes to Dm. Solo half is Dm, then half in Am, then back to Dm for the verse, and repeat the previous structure. The outro is all of a sudden in Dm
The Clairvoyant - Starts in D major. Verses and chorus in D minor. Solo in E major, for a bit E mixolydian, then verse and chorus repeats, before they do the Seventh So trick (something they only really did on this album). They move the chorus down two semitones, in this song, from Dm to Cm after half of the last chorus. Outro in D major, same as intro.
Only The Good Die Young - Starts in Em. verse in Em. Chorus repeats the trick from the previous song, shifts down two semitones to Dm. Then, after half of the chorus, it moves to Fm. Solo 1 in F# Frygian. Bass solo, riff, and verse in Em, before repeating chorus in Dm, Fm, and solo 2 in F# frygian. The first part of the rock outro is in F#, while the second part is in Em. The outro is again in Em.