You've finally gotten your big break. It's a production contact of a major show filled with important people... but you've been offered the swing.
Before we delve into the "should-I-or-shouldn't I" of swinging, let's define exactly what a swing does.
A swing covers the ensemble, so if anyone in the ensemble is out, you will be "swung" on. Usually a swing covers a certain number of tracks within the ensemble. (Only the dance captain knows all of them.) Depending on the needs of the show, there may be a singer swing or a dancer swing, or more than one of both. Typically, the swings also have to cover any character parts and features within the company.
A swing is different from an understudy in that an understudy covers principal tracks. However, a swing may also understudy principals. (I did-- more than one.) A swing is different from a standby. The standby covers one or more principal tracks off-stage. He or she will never do ensemble, they simply show up at the theatre just in case. Most big Broadway shows (Hamilton, King and I, Wicked) will have standbys for the leading roles as well as understudies within the ensemble. After all, the show must go on! If you're offered an ensemble track covering a principal, you may want to find out if there's a standby, how many covers there are, and if they designate first cover from second cover and so forth. (You may not be able to find out the latter in any official capacity. After all, if you're a first cover, they would have to pay you more, wouldn't they? What you can do is open up a program and see how many people cover a track or stand by.)
But I digress. I used to think that every person pursuing a musical theatre career should be required to swing. Like a theatrical version of compulsory military duty.
But, having done it, I no longer think that. It's too hard. Not everyone can swing. Some people would be terrible at it, and the show would be a disaster.
If you're hired as a swing, you have the toughest job in the show. You're being hired because you can fit into more than one track. You're versatile. And somebody thinks you're smart, not to mention organized and talented. If the cast is seasoned enough, they will know to treat you with respect bordering on adulation. And they should! On more than one occasion, you're going to be called upon to save the show. It's a heck of a job.
As a swing, it's easy to feel like a second-class citizen, especially at the start of the process. You'll be on the sidelines in rehearsals and tech. Your costumes will probably get done last. You won't get to participate in any promos or awards shows unless they shove you on at the last second as a courtesy. You won't get to take a bow on opening night. And since you're not on stage every night, it's easy to feel left out.
However, there are perks. In addition to being the aforementioned hero of the show, you are making yourself indispensable. If you do it well, you're establishing a reputation among stage managers, directors, and dance captains-- people who may very well have casting power in the future. For dancers, it's an excellent avenue to pursue if you'd eventually like to choreograph. (Swinging is also easier on the body for dancers, due to less repetitive strain.)
It can be thrilling! Your first few nights swung on will be filled with adrenaline. You may make a few mistakes, but your cast members will rally around you, and "shove with love." After a while, the feeling of otherness goes away. You're very well paid because you most likely cover a lot of features and specialties in addition to your swing duties. In a long-running show, you won't get bored doing the same show every night, and you frequently won't have to do the show at all. On those nights, you can go home early, usually after a pre-determined musical number in the second act.
So if you're a smart, adventurous, versatile performer who loves the adrenaline rush that comes with saving the day, do it! But if it's going to eat away at your soul not to be on stage every night, you may want to pass. It's also very easy to get caught in the swing "trap." If people know you do it and you're good at it, the industry might start to look at you as a swing before anything else. (Remember, this is because good swings are incredibly valuable.) However, maybe you just want to do it this once, for this show in particular. That's fine. If future swing auditions come your way, feel free to tell your agent you'd prefer an ensemble track.
The only aspect of swinging I found truly irritating was when ensemble members would come to me for some sort of absolution. It usually started with a heads up. "I'm not feeling too well, so I may call out tomorrow if I'm not better." That's fine. But the people who started to give me a lot of reasons why they couldn't go on, or frequently called out and felt the need to apologize to me before, during, or after, bugged. I actually don't care why someone can't go on. If you're out, you're out, and it's my job to go on, not to judge you for it. But it is not my job to smooth over your guilty conscience. I'm not going to be mad at you for missing, but I am going to be annoyed if I keep having to reassure you that your work ethic isn't shitty. Take that issue somewhere else!
My final piece of swing advice? Due to the large amount of sweets backstage, and the relative amount of free time you'll have on your hands, tell yourself to stop eating at curtain. Even birthday cake! (Especially birthday cake, unless it's yours.) Otherwise when it's time to put on those costumes, you may find they don't fit! #beentheredonethat