Also:
* "Concert pitch" of A=440Hz is not universal.
* 12 tone equal temperament is not universal.
* Analog playback systems often run at slightly incorrect speeds.
* Some instruments are difficult or impossible to tune, so the tuning will vary with temperature. Nobody is going to tune a pipe organ in a drafty church every time the weather changes.
* DJ mixes rely on playing tracks at different speeds to allow for smooth transitions between tracks of different tempo[0], which changes the tuning.