Bind metadata to a Clojure function without a var via defrecord

gistfile1.txt

Via clojure.core, metadata associations are only available to vars.
This is a method to associate metadata with lambda functions,
perhaps purposely exposing data a function closes upon, as encapsulation
is the *only* supported behavior for closure data.

(defrecord MetaFn
    [md f]
  clojure.lang.IFn
  (applyTo [this args]
    (apply (:f this) args))
  (invoke [this]
    ((:f this)))
  (invoke [this x1]
    ((:f this) x1))
  (invoke [this x1 x2]
    ((:f this) x1 x2))
  (invoke [this x1 x2 x3]
    ((:f this) x1 x2 x3))
  (invoke [this x1 x2 x3 x4]
    ((:f this) x1 x2 x3 x4)))

(defn db-env-init
  "returns an envelope function chain, closing on the envelope, and adds a decibel to linear post-processor function.
  adds envelope points as metadata to returned function."
  [envelope-fn]
  (->MetaFn
    (-> (envelope-fn 0)
        :points)
    (fn [n]
      (comp
        db->linear
        (-> (envelope-fn n)
            prepare
            realizer)))))