Rehearsing an opera starts round a piano. The principals learn their parts at home and come in to have coaching sessions with the conductor and the repetiteur (the pianist). Both these people will know the opera off by heart; they'll know how it's going to be paced and how each note should be sung. Some singers say performing at the Royal Opera House (ROH) is worth it for the coaching sessions alone.

Then the rehearsals move into a studio. This will normally be as big as the stage and bits of the scenery will be set for the rehearsal: stairs, for example, or tables and chairs, even a sloping floor if that's going to be used. Things they can't set, like the enormous castle walls in 'Tosca', will be marked off on the floor with coloured tape – so the singers get used to the area they'll be performing in.

The Wardrobe don't usually let singers practise in their costumes (there would be too much repair work involved). Instead they run up rehearsal clothes such as huge practise skirts for the women, and cloaks and coats for the men; getting used to wearing these things is important, as it can have a big effect on the way you move round the stage. The Prop Department appear with all the props. These are the sort of things you'd expect - goblets, lanterns, fibre glass food - and some you might not: a severed head (for 'Salome') and rows of little wooden houses (for 'Die Meistersinger'). Weapons all come from the ROH’s Armoury and the Armourer keeps a very close eye on them. Many of the swords are antiques and he doesn't want them getting chucked about. Safety’s very important too. When guns are used, although they only fire blanks they are still potentially dangerous, so the Armourer supervises their use very carefully.

At the front of the studio are rows of desks: one for the director and his assistants, one for the stage management team – who'll be noting down every move and working out which side of the stage the props should go – and one for the conductor. The music at rehearsal is played by the pianist (called a repetiteur in opera), but the conductor is still there to beat time and guide what’s going on.

Obviously the singers want to get used to their costumes and props but the most important thing about studio rehearsals is working out the moves: not only where you go on stage, but why you move at all. If you know why, for example, you're picking up a fruit knife in 'Tosca', you'll pick it up properly. So the director and singers spend a lot of time working out the sub-text of the show. This isn't written down, it's something you sort out yourself and is supposed to be the thoughts and feelings that are going through the character's head. So, when Tosca grabs her fruit knife, she isn't thinking, "Ah a useful knife to peel an orange with…" She's thinking, "Aha! A knife! Just the thing to plunge into the wicked Scarpia's heart…" It makes quite a difference to the way she picks it up.

Once the basic moves are sorted the stage begins to fill up. The chorus are called for their scenes, the dancers for theirs. Sometimes there is a pack of children to rehearse, or a troupe of acrobats. And all the time the director, the stage manager and the conductor are making notes. We'll need a spotlight downstage, we'll need three stage hands at least to wheel the dungeon off, I must remember to tell Miss So and So not to hurry that aria…

The last week of rehearsal is spent on stage. Now it's a question of working with the real scenery and costumes, making sure the doors work, and coping with the wings. The wings are the side of the stage; they're invariably dark and full of things to trip over - scenery, props, stage crew, chorus and electric cables.

Other people will begin to rehearse: the stage crew will be pushing the scenery on and off, the men in the flys will be getting the flat scenery up into the fly tower above the stage and down onto the stage again. Somebody might have to joggle the snow bag to provide a nice shower of snow or turn the wind machine to make a chilly whistling noise. The sound department will be trying out their sound effects, the off-stage musicians will be trying to find some bit of the wings where they can play their instruments and read their music – and the lighting department will be in. The lighting people - LX is the theatrical name - often make the show. They create the shadows, the atmosphere, the glowing colours and the dramatic contrasts on stage. During the 'Peter Grimes' rehearsals one whole session had to be given over to the technical people, so they could learn to raise and lower the floor and slide the walls in time to the music.

Finally the orchestra appears. As soon as they turn up, the director hands over to the conductor, who is now in charge until the first night. He usually calls a sitzprobe (a sitting rehearsal) in which the singers sit on rows of chairs on the front of the stage and sing the whole show through with the orchestra. After that come at least two stage and orchestra rehearsals, in which the show is run its entirety. The conductor may stop and start them, but that will be for musical reasons. All the staging should be perfect by now. Of course it isn't, and the director will often rush on to the stage to correct things, but he/she has to make sure they're not getting in the conductor's way.

The final rehearsal is the Dress Rehearsal – or General as it is called in the ROH. This is the final run-through and is usually played in front of an audience. The audience are Friends of the Opera House, members of the company and banks of photographers – who want shots for the national newspapers. There might still be a bit of tweaking to do at a Dress Rehearsal but, usually, it runs just like a show and the company is at last ready for the First Night.