Listen to any pop-music diva these days, and you hear melodies spinning every which way, like the hand-held shots in an action movie, wiggling and jiggling in a way that can give you a kind of aural queasiness, seasickness for the ear, unable to find the still point of gravity.

This style of singing has become the lingua franca for such popular music venues as American Idol and The Voice. The singer hovers around the expected note without ever having to land on it any more than an Apache helicopter touches down to disgorge the troops from its inside before soaring off into the ether once again.

This was not an issue in the past, when listening to Ella Fitzgerald, Peggy Lee or Dinah Shore. Whatever vocal calisthenics they indulged in were anchored to a harmonic rock that led the music to a distinct place — usually the final perfect-authentic cadence, the great dominant-tonic resolution.

But this is gone from most contemporary pop music. I don’t want to sound like an old fogey lamenting nostalgically about a golden-age past, for after all, there were good and bad singers then as there are now. But I do want to express something genuine about the progress of popular music. And to point out that in this, it follows the same pattern as that of classical music.

In his great Harvard lectures, Leonard Bernstein talked about how the history of music is the history of seeking “newer and better ambiguities.” And these ambiguities are often (though not exclusively) harmonic.

Consider the opening of Wagner’s Tristan und Isolde, with its famous “Tristan chord.” What key is that in? You can hardly tell, it wavers so ambiguously. But a look at it over the longer stretch of the score and you can discover an overriding structure of A-minor. The music stretches the meaning of tonality, but doesn’t leave it.

Debussy and Schoenberg, in different ways, undercut the pull and power of harmonic direction, softening up the basic tonics or dominants with extra harmonics: sixths, ninths, elevenths. The reason Debussy sounds so vague is that his harmonies are vague. His melodies remain clear as a bell, but they are built on shifting sand.

In jazz, the course of things went much the same way. Listen to Louis Armstrong, or — especially — Duke Ellington, and you hear the steam locomotive drive of the harmonic motion. Ellington built some of his most powerful music on the blues changes. They are hidden under a rich palette of tone color, but they are still there, providing a solid skeleton for the music.

But, beginning with the bop musicians, the extra partials have been once again added, to build harmonies more ambiguous and malleable. Sure, underneath it all, you can still find the basic harmonies of I Got Rhythm, but over the top, Charlie Parker and Dizzy Gillespie are playing those ninths and elevenths, letting the air out of the pneumatic drill of harmonic progression. So that, nowadays, harmonies have become mere ornament for elaborate melodies. You can ornament the tunes various ways without changing the basic tune — much like you can decorate a Christmas tree in many fashions.

When Schubert wrote a song, the melodies are unforgettable in part because they are constructed on persuasive harmonies. You cannot imagine Die Fiorelle or Erlkoenig reharmonized without also losing the melody: They are no more separable than height and width in a drawing. But take any tune from Andrew Lloyd Webber and not only can it be reharmonized with no loss to the music — whatever music there is — but it is absolutely expected that an arranger will change the harmonies. They are no more than ornament to a fixed melody. What was once the structural underpinnings of song have become merely the “changes” that we deck the song out with. The powerhouse dominant-tonic motion has been gutted.

You can hardly hear them anymore. In pop music, you hear a stepwise bass motion that plays more as a simple counterpoint to the melody, rather than a solid drill sergeant bouncing the heavy tread of root position tonics and dominants.

It isn’t that the heavy tread of Schenker analysis is the only way to organize music.

But all art exists in the play between expectation and surprise. If we expect a G7 dominant to resolve into a C-major chord, then the composer can play with that expectation and withhold the resolution, to draw out our longing for the satisfaction we will get when the final C-major is achieved. You can organize a whole symphony like this: As Bruckner’s Fifth heads slowly to a solid B-flat or — most famously — Beethoven takes us from an unsettling C-minor to a triumphant C-major in his Fifth Symphony.

But if you take away that rock on which most Western music has been built, you still need something to stretch out our longing and expectation.

It must be admitted that harmony is only one way to organize music.

Pop music has left behind the principle of its birth and begun to find new — and largely non-Western ways. Western ears have not heard so much Oriental melisma since the Arabs conquered Spain. Mariah Carey is closer to a muezzin than to a big-band singer. “Just hit the damn note,” you want to scream, but, of course, her artistry is to make us wait in anticipation of the final pitch of a note. That pitch anticipation has replaced the dissonance and resolution of harmonic tune-writing.

One style is not better than another. And I don’t mean to sound like I’m prescribing a return to the past.

But it is important to know what we have lost. The glory of 250 years of Western music is its unique experiment with harmony. We have tossed it away like a used candy wrapper.