Why does the oboe tune the orchestra?

Answer 1

It is generally believed that the Oboe is used as the pitch source to tune the orchestra because, of all the instruments, the oboe has the least ability to be varied. In this way of thinking, the oboist makes their reeds and strives to be able to play in tune, and since they can't be adjusted, whatever the oboist comes up with is what everyone has to accept and adjust to. There may be some truth to this legend.

On the other hand, the oboe actually has a fairly large range of variability if the reed is well made and the oboist is professional-grade. (Consider this: If oboes were so impossible to tune, how could a Berlioz symphony employ four of them?)

In actual fact, today, most orchestra musicians are already well-tuned to electronic tuners before the oboist sounds the first note, and the oboe-note/tuneup session is more for show than for real tuning.

Answer 2

The oboe's open note, that is the note played with no fingering, is concert A, so it is used as the note to which other intruments tune. The concertmaster tunes to it as well, and then in turn the remaining strings tune to the concertmaster.