I’ve run into this problem, though infrequently. It’s annoying in the United States because some instruments I play simply cannot be tuned that sharp. Flute is the biggest problem; you can only shorten the pipe so far. The organ where I often play is at 442 Hz, assuming normal comfortable room temperature. My trumpet tuning slides are almost all the way in, leaving little room for further adjustment. Musicians in Europe, where in some places A = as low as 432 Hz not 440, have it easier tuning down.

Cents are different from Hertz. One cent in music is 1/100 of a semitone. That’s quite a small interval. Most people cannot distinguish a difference of less than six cents. I can get down to four easily, which is kind of a game I play with audio engineers in the studio. Charlie is correct: 440 Hz to 443 is a difference of 11 2/3 cents. Quite easy for any musician to be bothered.

If I need to adjust a file a few cents, like a backing track recorded on a tape recorder whose speed wasn’t perfect, I use a stereo audio editor as mentioned above. Then I record to that track.

ps: for a fun read, look up why some people want the mostly standard A = 440 changed to A = 432.

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