The Collaborative International Dictionary of English v.0.48:

Orchestration \Or`ches*tra"tion\, n. (Mus.)
   The arrangement of music for an orchestra; orchestral
   treatment of a composition; -- called also instrumentation.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Instrumentation \In`stru*men*ta"tion\, n.
   1. The act of using or adapting as an instrument; a series or
      combination of instruments; means; agency.
      [1913 Webster]

            Otherwise we have no sufficient instrumentation for
            our human use or handling of so great a fact. --H.
                                                  Bushnell.

   2. (Mus.)
      (a) The arrangement of a musical composition for
          performance by a number of different instruments;
          orchestration; instrumental composition; composition
          for an orchestra or military band.
      (b) The act or manner of playing upon musical instruments;
          performance; as, his instrumentation is perfect.

   3. The act of using instruments to measure or control the
      behavior of an object, as a patient in a hospital or a
      machine being tested while under development.
      [PJC]

   4. The act of furnishing or attaching instruments to/
      [PJC]

   5. The set of instruments included in a system; as, a
      harvester with modern instrumentation.
      [PJC]

WordNet (r) 3.0 (2006):

instrumentation
    n 1: an artifact (or system of artifacts) that is instrumental
         in accomplishing some end [syn: instrumentality,
         instrumentation]
    2: the act of providing or using the instruments needed for some
       implementation
    3: the instruments called for in a musical score or arrangement
       for a band or orchestra
    4: the act of arranging a piece of music for an orchestra and
       assigning parts to the different musical instruments [syn:
       orchestration, instrumentation]