Perhaps you and I define "really significant meaning" differently.
It seems to me you might as well assert that poetry in the mind of the poet is only significant if printed on a page.
A melody arising in the mind of a composer, songwriter or Jazz improvisor has a life of its own. The elements comprising its structure -- intervals, use of space, rhythms, etc. -- possess inherent qualities that have the power to affect and modify physiology, emotions and mental states. While we tend to focus upon the larger aspects of structure -- an entire melody rather than its constituent intervals, for example -- it is those particular elements, occurring moment to moment that are modifying our physiology, emotions and mental state, whether recognized or not.
Perhaps this is more evident to those of us who play instruments.
For example, when playing a guitar solo over a progression, whether in a room with other players or at home to a recording, my experience has been that at a certain point, I’m hearing melodies and reacting to them milliseconds before playing them; it’s as if the music is playing me, or as the Dead put it, "the music plays the band". At such times, I feel the impact of the melody before it rings out into the air and strikes the ear-drums and its’s impossible to pull apart the emotion from the elements of pitch, intervals, rhythmic aspects etc.
Perhaps there exists no corollary for those who do not play but consider this: as a listener, If you hear a melody on a recording and later "re-play" it in your head, does it lose its "significance"?
I don’t know how relevant any of this might be in the context of audio.