Band versus Solo Piping
When pipers are playing together, it is obvious that they should all be playing the same low A (and ditto for all the other notes). On the other hand, solo pipers can have, within reason, any low A as long as the relative frequencies of the other notes to low A are correct.
But what is, most commonly, the pitch or frequency of low A? [On this website we will treat the terms as meaning the same thing, even if this is not strictly correct.] As is well known to most pipers, the bagpipe low A is not the same as Concert Pitch (the frequency, generally accepted as 440 hertz, of the note A above middle C in Western classical music. A major source of confusion (one of many!) for pipers trying to understand the musical scale of their instrument is that the base note of the scale is called A whereas in Western music, the basic scale (without necessitating sharps or flats) is called C major. But we will ignore that for the moment.