@lily i... I want to contend that 'middle C' is usually thought of as a _note_ / _tone_, which _has_ a frequency, but is itself better defined as the sound that results from a pressure wave _of that frequency_, and not just the frequency itself as an abstract unit?

If I play a middle C on a piano, the middle C isn't some frequency, it's what I _experience_ in response to a wave that _has_ a frequency as a property?