Michael Dilthey just finished writing an accordion solo "Sonata for solo accordion". You can listen to a recording on youtube: https://www.youtube.com/watch?v=l8eCB6S5Fig
Michael Dilthey received a doctorate in music composition from Northwestern University. He heads the music department at Massachusetts College of Liberal Arts in North Adams, MA.
I met him in 2014 when my trio gave a performance at his school. I asked him to write a solo last year, and he wrote this sonata. I like it.