Audacity won’t actually change the pitch. I’ve heard of this happening to a rock & roll singer at very loud volumes. He thought he was singing in-pitch but he was off when he listened to a recording of the performance at “normal” volume.
If you boost the levels to the point of clipping (distortion) you generate harmonics. That changes the “tone” but the perceived pitch should be the same. Or for example, a 440Hz sine wave and a 440Hz square wave will sound different and you’ll clearly hear the harmonics of the square wave but they should be perceived as the same pitch as A(4) on the piano.
You can’t do this easily with Audacity, but it would be “interesting” to play two tones at once (at different volumes) and then alter the pitch of one tone until they sound like the same pitch.
…I listened to a special test-recording once that indicated I was hearing different pitches in my left & right ears! It’s not something I’m aware of and it doesn’t affect my enjoyment of music. (I’m not a singer or musician.)
I’m going to try to make time to play with this some more in Audacity.
Here is my task.
I got hearing aids about a year ago. All year I’ve struggled with music sounding awful. In the frequencies not far above A-440 everything sounds badly out of tune, especially if it contains intervals that span an octave or more.
To my ears, on our piano (in tune to my wife’s ears) for the octave C-6 (1047.502) Hz and C-7 (2093.005) the latter pitch sounds decidedly ‘sharp.’ Moving down the keyboard from C-7, A-6 (1760 Hz) is slightly flat of a perceived octave and B♭-6 (1864.655 Hz) is still slightly sharp. This brought me to Audacity where I was certain I could do quantitative comparisons, or so I thought.
This explains my amazement this afternoon when I adjusted the gain on the 1000 Hz sine tone and heard an apparent shift in the pitch. It was a chance observation. I was working on the observation that, for 2 tracks, say 1000 Hz and 2000 Hz, both generated at the same amplitude setting, I could hear only the 1000 Hz signal until I adjust its amplitude downwards and 2000 Hz can also be heard.
I hope to post more observations in this thread as I find time.