Could go here; could go in Cafe Society, but these are factual questions I’d like the answer to.
When playing at a sporting event in which both teams have marching bands, how does each marching band know when to play, and when to shut up and let the other band play so they’re not playing over top of one another?
How do they know what to play at any given time?
For the halftime shows, each band has half the time (IIRC, the away band plays first, then home). They play the songs they’ve rehearsed, in the order they rehearsed them.
During the game when they’re in the stands just providing ambient music, the director or captain or other person in charge calls out a song, everyone flips their music folder to it if they don’t have it memorized, and they play. Usually this happens right after one’s team does something good on the field, so both probably wouldn’t start at the same time, but if they do, well, so be it.
What would happen if the players tried to take the field, but the marching band refused to yield?
Stanford loses?
It means that was the day the music died. Now if I could find a Chevy and drive it to the levee.
When I was in the marching band 30 years ago there was only ever one marching band. I don’t think I ever saw a second band at a football game, even the UWV games that I went to.
I can’t imagine there’s time for two bands to perform at a halftime show as they are only 15 minutes or so aren’t they? We were always ready on the sidelines 5 minutes before the half and our show was around 10 minutes long.
As for knowing what to play, we had a school flight song that got played after scoring. For other times we would get told what to play, which was usually just a quick part of a song. That was the band leader’s choice, though sometimes a couple of people would just randomly play something.
Like Chronos said, halftime is pretty tightly scripted. Visiting band first was the convention everywhere I played.
Presence of both bands must depend on where you are. I went to high school in Texas in the late 80’s, and I was in the marching band. We went to every game - home and away. Both bands performing their on-field shows at halftime was completely normal, to the point that I can’t recall any games being otherwise.
In the early 90’s I was in my college band; we performed at every home game and some road games. Out opponents seemed to behave similarly, so one- and two-band halftimes were both pretty common.
It was tight, but both shows could be squeezed in. In college, I believe a football team could incur a penalty if their band wasn’t off the field by the appointed time. Since the visiting band (if present) went first, it was always the home band up against the clock. And if the visitors overran their time, leaving the home band less time than planned - it was too bad for the home band. I believe we had to cut at least one show short because of this. The football game was definitely the priority.
As far as the bands coordinating playing “incidental music” from the stands during the game, my memory is a little more fuzzy. I’m not sure how it was handled in high school. In college I want to say that there was a convention for extended pauses like time-outs - home band gets odd-numbered quarters, or something along those lines. After a score, the scoring team’s band “had the floor” without exception.
In college, our conference had a rule that bands could not play during action on the field, including the huddle and pre-snap periods. So except for extended pauses like time-outs, we were restricted to really brief periods of playing. Our band had specially arranged a dozen or so “tags”, as we called them - 15-20 second snippets of oft-played tunes. These were called out by number and squeezed in between plays seemingly at the director’s whim during “our’” quarters (or the whole game, when we were the only band).
After our team scored a touchdown, we would immediately launch into our school’s fight song. The tune was long enough that it usually wasn’t over by the time the PAT attempt was lined up - on our director’s signal we’d get extremely quiet while continuing to play, rising back to normal volume as the kick sailed (hopefully) through the uprights. This was apparently sufficiently compliant with the “no playing during game action” rule.
In high school there was no such rule. Our practice was to generally only play the fight song at appropriate moments during the first half, basically keeping our eyes on halftime. Halftime was, from the band’s perspective, a dress rehearsal for the marching band competition performance. We’d normally take the 3rd quarter completely off, and then return for the 4th quarter where we’d explore our repertoire book a bit (always prepared to stop mid-piece to launch into the fight song when on-field events warranted). And like I mentioned earlier, I don’t recall how the bands avoided playing over each other. Possibly some hand-signal communication between directors that I was too oblivious to notice.
At all levels, tune selection in the stands was communicated from the director/drum major either by hand signal (e.g., a raised fist for the fight song) or simply shouting it out and letting it be passed back by word of mouth.
A good performance at the marching competition in late October was the object of everything we did all season - and if a band did well they could advance to subsequent rounds. Once we were done with competing, the atmosphere (for us) at football games lightened considerably. Most significantly, our marching rehearsal time dropped dramatically to “maintenance-level” and the time began being spent indoors preparing for the concert band season (which had its own competition in the spring).
When I was in the marching band, while in the stands (and the band had its own stands, a literal “bandstand”), the director would tell the drum major what to play, the drum major would tell the drum corps what the number was, then they’d play the intro beats, which was the signal to the rest of the band. Each snippet of song (usually one or two phrases from a longer piece) would have its own drum intro.
I only marched in high school. There was a strict rule against the band playing while the team played. At half time, both bands would always play—away first, home last. This was a conference with small schools scattered across the county. Bus rides were never more than an hour.
This:
I think the OP is asking about when the bands are in their seats, not halftime shows.
Usually, the songs are pretty short. They play the school’s fight song when their team scores. When I was in band, we always turned down the volume for the extra point, then went back to full volume. Other times, the songs are pretty short, usually less than a minute, and played when there’s a lull in the action, like when the referees confab over a call. When the refs start to announce their decision, the drum major cuts the band off. Breaks between quarters are also when the band will play.
Whenever there’s a visiting band, the home band usually tries to observe some kind of courtesy and hold off when the other band begins to play, but that sometimes that doesn’t happen, especially if it’s the traditional rival.
As for what we know what to play, we’d been rehearsing a playlist of 5-6 songs. The drum major screams the title, or the percussion section plays an intro that identifies the song for the horns to join in, like the classic MGM drum rift. (Dum dum. Dum dum. Dayalatalatalatalata dum dum) We had 2 fight songs at NCSU and shortened versions of popular songs. You’ll hear a lot of college bands play “Seven Nation Army” by White Stripes nowadays, which I’m really tired of. I played sousaphone, so I was in the back row. We had to use lip reading skills sometimes when the crowd was too loud for the drum major.
Total nitpick, and I was never in marching band, but I think you mean the 20th Century Fox intro.
So this is really interesting to me. I did six years of marching band in Maryland. I never saw another band at a football game and we never went to one, even when there was a playoff game. Is this a Texas type thing, or more of a Western thing? I went to a D3 college so there weren’t a lot of visiting people at the games.
We also did competitions almost every weekend in high school, which might explain why we didn’t go to away games. But I know I’ve never seen two marching bands play at half time so it’s really strange to hear.
When I was at NCSU, the marching band always went to away games that were reasonably nearby, so Duke, UNC and Wake Forest were a given. We only took one weekend trip per year, either Clemson or Georgia Tech. So, 7-8 games per season had 2 bands at halftime. Any Division 1 marching band has a similar schedule.
The band member whose horn got flattened sold the “authentic” instrument more than once to collectors. This is funny if you know anything at all about the LSJUMB. 
When I was in high school (Cleveland), we went to all of the reasonably close games, which was almost all of them. There were even cases where schools used other schools’ stadiums for their home games (such as archrivals St. Edwards and St. Ignatius both using Lakewood High School’s stadium), so you could go to an “away game” in your own stadium.
In college (Villanova), I think we probably would have gone to an away game at a reasonably-nearby school, except I don’t think there were any of those in football in my four years. It did happen sometimes with basketball games (where the pep band played), but those were on neutral ground, in Philadelphia’s professional arena.
My own experience in high school band was that there were no formal rules, but there were three general guidelines.
As for half time shows: whenever both bands had shows that were longer than the allotted time, one or more would get truncated. I unfortunately don’t remember which band tended to wind up truncated.
Finally, when the two bands were around the same level, there would often be a “battle of the bands” dynamic, where one band would play, then allow the other to play. This mostly took place during downtime or at the end of the game. The way to end the battle was to play their fight song.
And, yes, of course, you played the fight song after every goal. And the drum line would play to help the cheerleaders.
Oh, and this is for football. Basketball, being indoors, basically didn’t allow playing when the game was live, and all you had time for were those little tags. And there was no halftime show. It honestly felt like a waste to show up, honestly, to the point we started only having a portion of the band there.
We always had time for full songs in college pep band (at the basketball games). But that might be because Villanova basketball was big enough to be televised, so they needed time-outs long enough for commercial breaks.
College and high school basketball are different. Even for relatively small schools, there will be at least radio coverage and a set number of longer media/officials timeouts during the game (about 4 per half, IIRC). Those would be long enough for full songs.
That’s aside from the timeouts called by each team, which can be much shorter.
Ah, right, I forgot about radio broadcasts, which would also need commercial breaks. Though I really shouldn’t have forgotten about them, because my brother-in-law does some of those broadcasts as a side gig.