When does an arrangement of another arrangement become yours? (if ever)

I am in the process of making something (for my own use) and thought, when I'm done I'd put it out there for others to use. However, I am not sure at what point the arrangement becomes mine.

I have come to love the song Lachrimae by Dowland though a book of arranged pieces for baritone ukulele by Michael Walker and decided I wanted to play it on the viola but couldn't find an arrangement, so I opened up Musescore and copied the arrangement by Michael Walker exactly as written but translated it to alto clef. Same song, note for note, different instrument and different clef. At this point, I assume its still Michael Walker's IP (is it?) as I haven't actually changed anything about the music. Then I went through and looked at the chords/dyads and changed/deleted many of them to make them more manageable on viola. Is it now my own IP? After removing many of the chords/dyads, I felt like a lot was missing so I thought it would be fun to turn it into a viola duet. Would the duet be my IP? Would all of this *not* be my IP because I started from another arranger's arrangement?

Based in USA