It's a film that, on paper, not only shouldn't have worked but might well have blighted a wide spectrum of careers, from Hollywood movie stars and British sketch royalty to Shakespearian stage icons. And that title, The Death Of Stalin, hardly suggested box-office gold. But trust director Armando Iannucci to wrangle that disparate cast, with their original accents, and create a modern classic.

In classical music circles the soundtrack also caused intrigue, meanwhile: had orchestra-buff Iannucci unearthed a great lost masterpiece? All will be revealed below, in the first Laugh Tracks, our staccato new series where music and comedy come together.

We're talking Stalin because on March 27th, London's Barbican stages a live screening, with the film's score performed by the BBC Symphony Orchestra - and a fascinating score it is. That's followed by an onstage Q&A with Iannucci, composer Christopher Willis, producer Kevin Loader and at least one of the cast, with strong hints of Michael Palin.

The man who put this event together is longtime BBC Radio 3 and BBC Proms host Tommy Pearson, who has produced numerous big in-concert screenings. So we got him on camera - well, Zoom - to talk comedy scores, art under dictators, and Jason Isaacs' medals.

Why are you doing The Death Of Stalin live then Tommy?

Well, the bottom line is I think it's a masterpiece. And I thought it was a masterpiece immediately I saw it. And I saw it many times afterwards.

That transatlantic cast with their own accents, the subject matter - in anyone else's hands it's a car crash, isn't it?

It's Armando Iannucci, I mean, they are just so good at this kind of thing. The Death Of Stalin already seems like quite a contentious sort of idea. I thought it was very, very funny, of course. But the thing that I was left with at the end, while the credits were rolling, I was thinking - and a lot of my classical music friends were also the same on this - 'What is this piece of Shostakovich that we have been missing all these years?'.

So I waited as I always do for the credits, and it just said 'music by Christopher Willis'. It never arrived, this Shostakovich piece - no credit. I thought, 'Wow!' And it turned out of course, that it was all Chris. I just thought it was amazing.

When did you decide to try to stage it?

It was last year, I ended up watching Death Of Stalin again on TV. I thought 'this music is so good, why don't we try and do it live?'. Matt Dunkley, who conducted the original film score and is conducting the live version, I've known for 25 years. He said, 'great idea, I'll put you in touch with Chris'. Chris put me in touch with Armando, we had a big zoom with all of us together, and I was very excited about it.

As I'm sure you know, Armando is extremely literate in classical music. I think he already probably knew me a bit, because he listens to Radio 3, so that's how it all came together really. I'm always looking for things to do.

It's always interesting how orchestras perform those scores, over the film - timing the live performance to the footage must be quite a challenge too?

One of the privileges of putting these projects together is I spend a very long time with these films. Not only do I watch them probably 60, 70 times, but also, individual scenes that have the music in, working on the music synchronisations to such a degree, you get to know every little rhythm of everything. And what I like about that, when we come to do the rehearsals, I will know precisely if something is slightly out or not. Because my brain has learned the rhythm of the speech.

Timing is particularly important in comedy.

That is particularly the case with comedy, yes, everything minutely timed to perfection. So it's a learning curve. I mean, what I love about it is I learned so much about the art of filmmaking, particularly editing, and pacing. It's fascinating and of course, both of those things are so crucial to comedy. With this film, I just love the performances. I mean, everything Jason Isaacs says makes me roar with laughter.

It definitely bears repeated watching, there are so many lines you could miss...

My favourite line in the whole movie is 'Right, I'm off to represent the entire Red Army at the buffet'. But there's another line in it which made me roar and I was the only one in the cinema who did, because it absolutely hit the right spot, for the classical industry.

When the reserve conductor is interrupted at his house and the guy says, "Maestro, you are Moscow's finest - and closest - conductor". There's so much truth to that; it happens, where you have to find someone who's available but quite nearby. It's almost like a throwaway line, but it could only have been written by someone who understands that. The detail in it is totally wonderful.

The most famous bit of the score is Jason Isaacs' introduction as Marshal Zhukov, which is spectacular. If I was him I'd play that 30 seconds of music every time I entered a room.

It's actually only 12 seconds! A big fanfare, he gets his coat off, and then he pulls his jumper down, his medals. I had the version without music, because I have all the audio stems. You take the music out, all you hear is a sound effect of medals going 'jiggidy-jig.'

Jason always says that they had to tone that character down effectively, because the real one was so ridiculous. They didn't have as many medals on him as the original, because no-one would have believed them. So actually it's not quite as crazy as the real thing.

I think this is the first in-concert screening I've seen that's a comedy.

They tend to be dramas. I've done a lot of them now, and some of them have quite challenging audio, things like Independence Day, because that's a big effects movie, with music in it all the time. So what you tend to do is you put subtitles up. I'm not doing that here. Because comedy does not work with subtitles.

So this is one of the few times this music has been played to an audience - which seems quite mad, if it's so well regarded.

I certainly think, once we finish this, we will put another suite together so people can play it in concert if they want to. Because talking to people I know, in classical music, they all know this film, and they always remember the music, because it was so startling. And I know a few conductors who would quite fancy doing it.

This event, it must be great for the cast and crew to see the film again, as part of an audience.

I know Jason [Isaacs] a bit so I said 'we're doing this thing, fancy coming?', and I just got a one-word email back saying "apso-fucking-lutely". Which is very Jason. But he's shooting White Lotus in Thailand now, on a gorgeous beach, so he's sending us something instead.

One of the things I've noticed, I think the actors all really care about the movie - and actors don't always. It was very similar, I did Brassed Off with a live brass band - another comedy - and that was fabulous. But what you noticed was all the actors, it really, really meant something that they were in it. They still love it and they're still thinking about it.

I get the feeling about that with Death Of Stalin as well. It was one of those projects that everybody really thought meant something. Because, one of the things I'll probably talk to Armando about in the Q&A, is how it relates to now, because you don't make a movie like that unless you feel there's resonance now.

And even more since it was made. You'll probably not be doing a live score of it in Moscow.

Well, they did ban it didn't they? I'm not going there anytime soon, to be honest.

I saw a clip of Christopher saying that this score works almost like a Tarantino film, needle-drops which come in at particular moments, rather than just playing in the background quietly...

That fits the style of the movie doesn't it; I think that kind of comedy doesn't work if you've got music behind it. The way Chris uses the music, apart from the sort of action scenes, it's a bit more like the theatre, where it's a transition from one scene to another, and music would get in the way of the comedy. Although it's dark, it's very funny. And it just doesn't work if you put music underneath.

I think Airplane is a really good example of how you can sell a joke through music. The reason why Airplane works is because everyone involved in it is treating it like a serious drama. That's exactly the same with Elmer Bernstein's score, it's a straight-ahead dramatic score. That's why it's funny.

That's right, it's very grand isn't it, so you'll get a silly joke followed by this huge fanfare, which is really funny but also brings you back to the drama...

Chris has to do that in this film because so much of the time in Death Of Stalin, the comedy comes from the absolute horror of it. What I thought was amazing about the film is that some of the things you think are funny, you go back and look at the history and it was true - you're laughing at this awful stuff.

Chris has to play it quite straight in that regard, there's no comedy in his music in that sense. The important thing about it is that he's taken on the style of mostly Shostakovich, and I think it grounds us. Because actually, if you think about it, that's actually the only authentic language 'voice' in the movie, because no one else is doing a Russian accent.

His musical language is pure Russian, so it grounds us in it, it gives us a time and a place in a very, very effective way; it's not just about the costumes and the setting. Although of course, the first music you hear in the movie is Mozart.

The film starts with that extraordinary scene of the live orchestra playing - which must be tricky to tally up with the orchestra on your stage?

Actually, no, I made some decisions on that. It's always hard to try and match music being played on the screen with music doing it live. I think one of the problems is it takes you a little bit out of the film. So what I've done is, the bit at the beginning where every time you see her [Olga Kurylenko as pianist Maria Yudina] playing on screen, we are not playing. And everything else with the orchestra playing, the soundtrack is on the movie.

So the BBC orchestra sticks to Willis' score - it's good to bring focus on it like this, as it clearly plays such an important role.

The important bit, I think, the music never gets in the way of the comedy. It's there for dramatic purposes, it's there to move you from one scene to another, but it does play during some of the big scenes where we see people being rounded up, all the horrible stuff.

I think part of that is because, so much of what we know about Shostakovich, for example, all of that horror, ended up in his music. That was his expression of it, there was only so much you could do as an artist under Stalin. If you were a favourite, fine. If you weren't, you could be in trouble.

The film - and the music - certainly bring that to life, the bizarre lunacy of it all...

All of these great artists were able to bring that horror to the music and bring it out in some ways. Shostakovich did it very often in an ironic way. It sounds bombastic and celebratory, but under it is utter terror. That's often the real power of that music.

I think Chris - because Chris is a music academic, too - he knows all about this stuff, he knows how to do it. And I think that's what he does in this film, too. He's able to take that idea and bring it into the film, which of course suits the film perfectly. Comedy and terror at the same time.

It's interesting watching these live concert screenings. For the first half I'm always really aware of the orchestra, then I get really into the film and almost forget they're there...

That's good, too. The reason for doing them, I always think, it's twofold really. Obviously you get to see the film. But it makes it an event. It's kind of an enhanced experience. You're not getting the same experience that you would if you go to the cinema.

It's just a great way of showcasing music and what orchestras can do. The response afterwards is often ecstatic and wonderful, because I think people have realised that not only are they amazing at what they do, but also there's a slight amount of trepidation: are all the marks going to be here? Is it going to work perfectly?

It's not just like pressing play on a movie, there are so many other things going on at the same time, it's almost like a challenge, particularly for the conductor. So I think at the end, people are left with a great feeling of euphoria because they've enjoyed the film, but also, that these guys have done this.

You probably won't want to hear this but one of the joys, deep down, is that added jeopardy, that something could go wrong...

Of course! It's live performance. And by the way, it does every now and then. But hey, that's showbusiness.