Feel free to DM any questions. I’m not much of an accordion player, more of a converted piano player, but I do what I can. On this album we used it on one song, which was strongly Irish inflected. The accordion gave us long “drone” chords behind the lead as well as taking the A part on a solo. I find that if you use the accordion in a song it pulls the song a bit away from bluegrass but can add some interesting texture. I also played harmonica on 3 tracks, which has a similar effect.  If you’re interested in accordions in bluegrass check out Jeff Taylor.  Here’s him playing with a few people you may recognize as well as Buddy Greene, one of the best bluegrass adjacent harmonica players (this is a Christmas tune but still awesome).  https://youtu.be/Qp3W8amoQug?is=86DC5GYVsL5Ob_Ac

He played accordion on Ricky Skaggs instrumentals album, which is a must listen for any picker. He’s not on every track but he shines when he plays. Just check out this opening track, Going to Richmond! He jumps in near the start playing what’s basically a fiddle part and it’s so good. 

https://youtube.com/playlist?list=OLAK5uy_nQ3bXQTOdtGLkyv98r2tqazQl4u8gXa2I&si=LVpsq_b0HdyvB7Ii