diff --git a/src/music.clj b/src/music.clj
index 13207ba..dd9995a 100644
--- a/src/music.clj
+++ b/src/music.clj
@@ -6,5 +6,17 @@
 ;; a duration is a rational number, e.g. 1/8
 ;; a note has a duration, optionally a pitch, and optionally any other necessary keys (e.g. loudness)
 ;; {:duration 1/8 :pitch [:A# 3]} is a note. {:duration 1/4} is a note (really, a rest)
+
 ;; (:=: noteA noteB) represents noteA played simultaneously with noteB
 ;; (:+: noteA noteB) represents noteA played followed by noteB
+
+;; what do the above functions return? Whatever that thing is, a note is a "subtype" of it
+;; since the :=: and :+: operations can be applied to their return values
+;; one solution would be to have [noteA noteB] represent noteA and noteB played sequentially
+;; and [[noteA noteB]] represent noteA and noteB played simultaneously -- this would
+;; mean that :=: and :+: would have to act on vectors
+;; this would allow arbitrary musical phrases, e.g. [noteA [noteB noteC] noteD], but what
+;; would deeper nesting mean?
+
+;; (modify noteA control) merges the control map into the noteA map
+;; control maps have keys like ::tempo, ::transpose, ::instrument, ::phrase, ::player, ::keysig