Plan the picture before you teach a single step

A large cast number is not really forty people learning forty sets of steps. It is one picture that happens to be made of people. Before the first rehearsal, sketch the number on paper the way a designer would sketch a set: where is the weight of the company, where is the eye drawn, where is the air in the stage picture? Decide roughly what the audience should be watching in each eight-bar phrase. That single habit saves hours later, because you will always be able to answer the question "why is she standing there?"

Sit down with your musical director and mark the landmarks — intro, first verse, chorus, middle eight, key change, final chord. Number the bars. If you know that the chorus begins at bar 33 because the MD counts it that way, the company will learn it faster and the band will forgive you far more readily when the staging shifts slightly in week three.

Divide the stage into zones

Forty performers on an amateur stage will bunch into a huddle unless you give the space a structure. Use a simple nine-zone grid: upstage, mid-stage and downstage, each divided into left, centre and right. Name the zones and use those names consistently, in rehearsal and in the notes you send out. Chalk or spike tape the grid before the company arrives for the first staging call, even if it only stays down for one session.

• Give each zone a job: soloist, counter-melody group, chorus block, dance feature, principal.
• Balance numbers across zones so no corner looks crowded and no corner looks abandoned.
• Spread your stronger voices so the sound reaches the back of the hall evenly.
• Use levels as well as positions — a chorus kneeling downstage left reads very differently from the same chorus standing upstage right.

Try not to place two competing moments in adjacent zones at the same time. If you have three featured singers, give them space, distance and different heights, and the audience will always know where to look without being told.

Give every performer a focus point

"Look at the audience" is not direction. It produces a row of polite, glassy faces. Every performer in a big number needs a specific target: the soloist's shoulder, the conductor's left hand, a mark on the back wall, the top of the proscenium arch. Eyes carry energy, and eyes pull attention across a stage far more powerfully than any arm gesture.

In each zone, name a leader — one reliable person the others can watch for timing and spacing. Ask everyone to rehearse with their peripheral vision switched on; if the conductor is visible from the wings, the company should be able to catch a beat without turning their heads. Even the performers standing in near-darkness upstage right must look invested, because a third of your audience will be watching them rather than the soloist.

Rehearse transitions harder than the poses

The most common failure in a large musical number is a beautiful final tableau in the chorus, followed by the entire company wandering into the next section like a bus queue. Transitions are the number. Give every move a specific route and a specific destination, and count the bars in which it must happen.

• Name the tracks — "crosses downstage right via the piano", "over the top and round the back" — so people can remember them.
• Walk the routes at half speed first, then at tempo, then with the music playing.
• Hold short "traffic rehearsals": five minutes, no singing, just travelling. They are tedious and they are worth it.
• Learn where the band is playing under dialogue or underscoring; that is where you can hide movement.

If two groups have to cross, send one upstage and one downstage and tell both groups which one has the right of way. Small courtesies like that prevent collisions in performance and panic in the wings.

Build the number in layers

Staggered calls keep everyone fresh. Bring in principals and featured dancers first, then the soloists, then the full company for the last hour. Teach the music in sections, then the positions, then the movement — or, for a heavily choreographed number, positions first and music afterwards. Either order works as long as you are consistent.

Record a rehearsal track so people can practise at home, and run a verse at a time before joining two together. Save the full run for the point in the evening when energy is still high. If a run has gone stale, stop, fix one thing, and finish on the best version rather than the last version.

Keep the company moving as one

Notes belong to the company as a whole wherever possible; save personal corrections for a quiet word. Before every run, do a physical and vocal warm-up plus a quick spatial reminder of the layout. Ask your zone leaders and any deputies to police spacing and levels — they will spot a sagging line long before you do from the back of the auditorium.

Finally, make sure stage management has a plan for entrances, quick changes and prop hand-offs. Numbers often collapse not because of the singing but because a hat did not reach the right wing in time. On the final run, resist the urge to tinker. Let them feel the whole thing, from first chord to last, as one company moving together — because that, not the steps, is what an audience remembers.