What is the difference between an understudy, a swing and a standby?

A long-running show plays eight performances a week, for months or years. Over that time, people get sick, get injured, take vacations, leave for other jobs and, every so often, lose their voice an hour before curtain. The show still has to go on, so every professional production carries actors whose job is to be ready to replace someone at short notice. Collectively they are called covers, and the different titles describe where they sit while they wait and what they cover.

The quick version: an understudy is onstage in another part, a standby is offstage covering leads, and a swing is offstage covering ensemble.

Understudy

An understudy is a cast member who performs a part in the show every night, often in the ensemble or a smaller role, and also learns one or more other roles. When the actor playing a covered role is out, the understudy steps into it.

That creates a knock-on effect, because the understudy's own part now needs filling. In a musical, a swing typically takes over the understudy's ensemble track. In a play without swings, the production may have to reshuffle, and some plays hire separate understudies who are not in the cast at all.

Understudies in musicals often cover principal roles that suit their type and voice, which is why ensemble casting for a big show can be as much about who could play the lead as about who looks right in the chorus. Many performers' first leading role on a major stage arrives this way.

In the UK, the usual word is cover, and a role may have a first cover and second cover, in order of who goes on.

Standby

A standby covers one or more principal roles and does not perform in the show at all unless they are called on. On a normal night, a standby is at the theater or, depending on the contract and production, close enough to get there quickly, ready to go on if needed.

Productions use standbys for leading roles where it would be impractical to have someone in the ensemble cover them: parts that are on stage almost the whole show, parts that need a specific voice or skill, or roles where the producers want a cover who is fully rested and focused on that one part. The standby has no other track to leave empty when they go on, which makes the switch simpler for everyone.

The job is unusual. A standby might go weeks without performing and then play the lead several times in one week. Staying sharp without regular performances, keeping the voice and the lines in shape, and feeling like part of a company you mostly watch from the wings are the real challenges of it.

Swing

A swing is an offstage member of the company who covers several ensemble tracks. A track is everything one performer does in a show from start to finish: every entrance and exit, each piece of choreography, every costume change, which props they carry, which harmonies they sing, where they stand in every number. A swing might cover four, six, eight tracks or more, sometimes male and female tracks both.

Swings are mostly a musical theater role, because big musicals have large ensembles with intricate, interlocking choreography. When an ensemble member is out, or when an understudy moves up into a principal role, a swing goes into the empty track.

It is famously hard. Swings may learn which track they are doing that night only hours before the show, or occasionally mid-performance, when someone is injured during the first act. They have to know not only their own moves in each track but where every other person on stage will be, since they are fitting into a picture that has been built around someone else. When things go badly wrong, a swing may cover parts of two tracks at once, called a split track, with the dance captain or stage management working out who does what.

Productions also sometimes have onstage swings or partial swings, who perform in the ensemble and cover other ensemble tracks; the exact titles vary between shows and contracts.

Alternate

An alternate shares a role with another actor on a fixed schedule. One actor might play six performances a week and the alternate two, or they might split the week more evenly. Alternates are common for roles that are extremely demanding vocally or physically, where nobody could safely play all eight shows, and for roles played by children, whose working hours are limited by law in many places.

The difference from covers is that an alternate's performances are planned. Audiences can often find out in advance which actor is playing, and the alternate is part of the regular rotation.

How covers learn the show

Covers usually learn their roles by watching. In the early weeks of a run, understudies and swings sit in on rehearsals and watch performances, often from the back of the house or the wings, writing down everything. Notation is personal and obsessive: scripts marked with every move, ground plans for each number with each performer's path drawn in a different color, notebooks of who is where on which count. Many swings keep a binder for each track. The blocking notation a principal actor uses is the starting point, but a swing needs to record it for every track they cover.

Formal training comes from the people who maintain the show after the creative team leaves:

• The stage manager keeps the official record of the blocking in the prompt book and often runs understudy rehearsals for plays.
• The dance captain, a cast member responsible for keeping the choreography consistent, teaches choreography to covers and replacements and gives them notes. Dance captains are often swings.
• A resident director or associate director, on larger productions, maintains the staging and the performances and rehearses covers in their roles.

Productions hold regular understudy rehearsals, where covers run their roles with each other, usually on the set but without an audience. Before a cover goes on for the first time, there is often a put-in rehearsal, a rehearsal of the show with the new person in place, sometimes with the full cast and costumes, sometimes with only the people they share scenes with. Put-ins are also how replacement cast members join a long-running show.

Covers are generally expected to be fully prepared by a set point in the run, well before the first time they are needed. Being off book in a role you might not play for months is the core discipline of the job.

What going on is actually like

For an understudy or standby, the call might come the day before, the afternoon of the show, or during intermission. There is usually an announcement or a slip of paper in the program telling the audience who is replacing whom. Then the cover plays the role they have watched a hundred times and maybe never performed with this cast in front of an audience.

The craft of it is staying faithful to the production's staging (so the other actors are not thrown, and the lighting finds you where it expects to) while bringing your own life to the role. Directors and stage managers want the show intact and the role alive, played by you. Covers who manage both build reputations quickly, and in an industry this small, a great night going on for the lead is the sort of thing people remember.

The advice from people who have done the job is consistent: prepare as if you will go on tonight, keep your voice and body in performance shape, and run your lines and tracks regularly even when nobody has asked. When the call comes, you will not have time to catch up. For a refresher on getting lines in fast when you need them, see how to memorize lines fast.

More questions