Trying to learn a song on guitar in an odd alternate tuning. How do I find the chord shapes?

Question

EDIT: I got the first chord and therefore the tuning completely wrong! This is going to make a lot more sense now that I realize the first shape is 10 10 9 5 5 5. So the tuning is really just DADGBD. Leaving my mistake below.

I'm a beginner-to-intermediate player trying to learn the song "Everyone You Meet" by The Clientele:

Live in-studio performance

So far I've figured out that the tuning is D# A# D# G B D, capoed at 5. The first chord is a C major played as 9 9 8 5 5 5, or 4 4 3 0 0 0 relative to the capo on 5.

The main remaining chords in the song are D, G, and Am--probably extended versions of each. My questions are:

1. Have you ever run across this tuning before? Why would you choose it? As I figured out the first arpeggio I was like, "Ah, this is going to be DADGAD," but nope, not even close!

2. How can I begin figuring out the shapes of the other chords? In the video it's obvious how he's playing the first chord, but I'm not seeing his fingering on the other chords clearly.

Thanks!

Answer 1

DADGBD I know as double drop D tuning. It is fairly common with open tunings. It gives the opportunity to play triads or 4 note chords on the top four strings, with I/V available on the strings 5 and 6. So quite versatile.

As far as the question is concerned: knowing the spelling of other chords will facilitate how fingering other than just a barre across the lot will work wonders. So, learn how to spell the other chords, and apply the adapted frettings to produce them.