# Can anyone help me understand F#ø7 - F7 - Asus - AM7 - D7 - Em?

I'm trying to understand what's going on in this small piece written for Genshin Impact game, the song's name is "Pure Sky" is about 1min long and you can listen to it here (the part I'm talking about begins at 0:27).

I believe the piece is in C major and here's what I can listen in this section:

I don't know for sure if I got that right (so correct me 👨‍🎓), so my question is about the last 6 measures:

1. I know some sort of modulation is happening, but where does that F#ø7 (or D7 without the D?) come from and why does it work?

2. After the diminished chord, what is going on here? `F7 -> Amaj -> D7 - Emin7` The `D7 to Emin` I imagine it's a Deceptive Cadence where D7 is a secondary dominant, but I'm not able to comprehend the `F7 to Amaj` movement.

3. As you can see I'm definitely not a professional musician, just a hobbyist trying to learn some funky harmonic stuff. That being said, I would appreciate (a lot) some material for studying modulation, chord substitution, chromatic movement in general, it could be books, blogs, videos, etc.

• Note: F#ø7 is a half-diminished chord, not diminished. The notes are F#-A-C-E. A diminished chord symbol is F#o for a triad (F#-A-C) and a diminished seventh chord is F#o7 (F#-A-C-Eb). Feb 16, 2023 at 2:27

`F#m7b5` is the `ii` chord in `E minor`, so the four measure from there through the `Amaj7` can be thought of as an extended subdominant in `E minor`, with the `F7` operating as a chromatic passing chord. (See, for example, What are the cadences in minor keys?.)
The `D7` (`bVII7` of `E minor`) is a common (in popular music) replacement for the `V` chord.