People talk about the negative effects of auto-tune on music, but I think it’s hard to actually spell out how auto-tune affects music from an aesthetic perspective.  All things considered, I think auto-tune can be used strategically at the right time and in the right way to achieve certain aesthetic qualities.  But I wanted to point out a specific way in which auto-tune detracts from the aesthetic and emotional quality of music.

As most musicians know, pianos are tuned to be relatively unbiased with regards to any particular key.  This becomes an issue, in part, due to the fact that “perfect” tuning is not technically possible.  Tuning the piano so it “works” in one key will tend to make it “not work” for another key.  So pianos are generally tuned to be slightly “imperfect” for every key, but equally so, so a pianist can play adequately in any key.  Pianos have to be tuned in this way, because pianists can’t adjust the tuning of the piano on the fly.

However, stringed instruments and voice can tune individual notes of a scale appropriately in such a way that produces useful emotional effects.  So, for instance, the 7th note in a major scale is oftentimes tuned a bit higher, because it can produce added tension before the note is resolved back to 1.  (E.g., a B is tuned higher than normal to make resolution to the C more satisfying).

For a more comprehensive illustration, the above image is a section of the jazz standard Sophisticated Lady, written by someone in the Duke Ellington cadre.  In the third line, one can see the A# (“some”) and the later Bb (“all”) are in some sense technically the same note.  However, a stringed instrument or voice may decide to tune them to fit the scale they are in.  Hence, the A# would tend to be tuned higher, to reflect tension and resolution to B natural, which directly follows it.  Likewise, the Bb could be tuned down (though this is because it would need to be tuned to the Db that follows it – which itself would be tuned lower in order to reflect tension and resolution with the following C natural afterwards).

The issue with auto-tune in a case like this is that auto-tune evens out both notes to the same note, which reduces the ability of the musician to use the emotional tension created by either tunings – and I would say, prevents the ear from cognizing the difference in keys presented by both notes.  So there you have it, a fairly clear and direct illustration of the way in which auto-tune affects the aesthetic and emotional quality of music.