Source : Webster's Revised Unabridged Dictionary (1913)

Tune \Tune\, v. t. [imp. & p. p. {Tuned}; p. pr. & vb. n.
   {Tuning}.]
   1. To put into a state adapted to produce the proper sounds;
      to harmonize, to cause to be in tune; to correct the tone
      of; as, to tune a piano or a violin. `` Tune your harps.''
      --Dryden.

Tuning \Tun"ing\,
   a. & n. from {Tune}, v.

   {Tuning fork} (Mus.), a steel instrument consisting of two
      prongs and a handle, which, being struck, gives a certain
      fixed tone. It is used for tuning instruments, or for
      ascertaining the pitch of tunes.

Source : WordNet®

tuning
     n : (music) calibrating something (an instrument or electronic
         circuit) to a standard frequency