system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Prior to playing, musicians tune their instruments to a specific note or small set of notes. Why do orchestras tune to A while bands tune to B♭?
gpt
Strings tune to A because every string instrument has an open A (they can play A without putting fingers down to change pitch) as one of their strings; by tuning that note, which is given from the oboe, the winds and strings are unified. Bands tune to a Bb because brass instruments are made so that Bb is the fundamental pitch (sounding Bb, regardless of the name of the note on that instrument). This means brass instruments can play a Bb without pressing down any keys. Woodwinds often tune to one these notes out of convenience; Bb is a crappy note for bassoon, for example, and so is F, the other common band tuning note, so balloons often will use A.