Musical instruments, like engines, are sources of propulsion meant to be manipulated by humans, theoretically to good ends. To take people somewhere else and bring them back (or, of necessary, to take them somewhere else and leave them there).
Like other machines, instruments are intended to be used for many differents purposes; mostly to please the heart, body or soul, one way to another. Or to irritate the mind, sometimes quite pleasurably.
Instruments are inherently unstable devices. They have to be tuned and manipulated (played) by a musician, when they may be steered to unheard-of musical heights, sometimes by accident.
More often, instruments are steered to already heard-of heights, wich can be pretty low. In any case, the instrument need not be restricted to established tonal capabilities, or even sound like itself; not all the time anyway.
Photo Stas Bepolit. Musical Instruments Museum
Based in a noted musician's decades of personal experiences, his book Solo Gig: Essential Curiosities in Musical Free Improvisation (CreateSpace Independent Publishing Platform, 2011) examines some crucial and far-reaching aspects of musical free improvisation, with particular regard to live performances. In this illustrated collection of narrative essays, the author looks both into and from inside this uniquely paradoxical, challenging and rewarding way of making music, within the context of an inherently eccentric milieu.