The Collaborative International Dictionary of English v.0.48:

Tune \Tune\, v. t. [imp. & p. p. Tuned (t[=u]nd); 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.
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   2. To give tone to; to attune; to adapt in style of music; to
      make harmonious.
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            For now to sorrow must I tune my song. --Milton.
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   3. To sing with melody or harmony.
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            Fountains, and ye, that warble, as ye flow,
            Melodious murmurs, warbling tune his praise.
                                                  --Milton.
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   4. To put into a proper state or disposition. --Shak.
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The Collaborative International Dictionary of English v.0.48:

Tuning \Tun"ing\ (t[=u]n"[i^]ng),
   a. & n. from Tune, v.
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   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.
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WordNet (r) 3.0 (2006):

tuning
    n 1: (music) calibrating something (an instrument or electronic
         circuit) to a standard frequency