@cleary I came to a similar solution, maybe a bit more "intuitive":
-- degree IV of the D major scale:
d1 $ n (scale "major" ("[-1,1,3]" + "4") + "d5") # s "superpiano"
-- simple progression (I IV V ii) in D major:
d1 $ slow 2 $ n (scale "major" ("[-1,1,3]" + "1 4 5 2") + "d5") # s "superpiano"
-- same as:
d1 $ slow 2 $ n "d5'maj'3 g5'maj'3 a5'maj'3 e5'min'3" # s "superpiano"
-- simple progression (I III v VII) in E minor:
d1 $ slow 2 $ n (scale "minor" ("[-1,1,3]" + "1 3 5 7") + "e5") # s "superpiano"
-- same as:
d1 $ slow 2 $ n "e5'min'3 g5'maj'3 b5'min'3 d6'maj'3" # s "superpiano"
It would be nice to have a dedicated function that could take also roman numbers for the degrees and a chord type (e.g. "maj" instead of "[-1,1,3]") but I'm really a beginner at Haskell 