Having suffered through many cases of determining what the correct pitch might be on a recording, I can safely say that electrical recordings made determination of that value a little bit easier. 50- or 60-Hz hum and harmonics thereof which are usually captured during the recording process give at least a benchmark by which pitch can be determined. Mind you, this process isn't fool-proof, since the power-line frequencies were allowed to vary somewhat during the day. However, the hum should at the very least tell one if an orchestra is tuning below or above 440 Hz. Often, it tells one a lot more!
Aaron Z. Snyder