I'd use |+ to make sure that the structure of the a4 (one event per cycle) has bearing on the rhythmic structure of the result (it doesn't in this case, because it aligns perfectly with an event on the left).
d1
$ slow 2
$ n (scale "dorian" "0 1 . 2 3 4 . 5 6 7" |+ "a4")
# s "superpiano"
I like to do this as a separate control, but that's down to taste:
d1
$ slow 2
$ n (scale "dorian" "0 1 . 2 3 4 . 5 6 7")
# s "superpiano"
|+ n "a4"