Well, I’m now writing an opera, and so I’m doing very little conducting, much less than I used to. This whole year I have just the concerts with the SWR Sinfonieorchester Baden-Baden und Freiburg and a short tour with Written on Skin, and that’s all.

The reason I took on the SWR-concerts was that they were the first orchestra to do a piece of mine abroad, which was in 1982, when they performed Ringed by the Flat Horizon – the piece that’s on this Munich programme – and they invited me to spend ten days in Baden Baden and attend all the rehearsals. That was, of course, an enormous thrill for a very young composer.

Then in 2005 I conducted them myself at the Strasbourg Musica festival.

They asked me back this time – and I very much wanted to go, because I heard this appalling news that the orchestra is being effectively disbanded. This is an orchestra with such a history; it’s been the most important orchestra for the contemporary composer for the past seventy years. They’re saying that it’s being amalgamated with the orchestra in Stuttgart, but still this is the end of its independent existence – and that this could happen in Germany is extremely depressing. So it was my last opportunity, and I instantly said yes.

There are three concerts, one in Freiburg, in their lovely hall there, their home. But first we go to Munich, where the Ernst von Siemens Music Foundation, who do fantastic work in supporting our art form, has started this adventurous new series (räsonanz).

After that we’re in Mannheim. In Freiburg we do Ravel’s Rapsodie espagnole and L’Après-midi d’un faune, and not the Haas piece, limited approximations; in Mannheim we have this extraordinary programme including Ligeti’s Lux aeterna and Messiaen’s Cinq rechants, as well as the pieces with choir from the Munich concert – Boulez’s Cummings ist der Dichter and Ligeti’s Clocks and Clouds – and the Debussy.

The programmes partly came about also because in 2013 I did some concerts with the Ensemble intercontemporain, and included on that tour were the SWR Vokalensemble from Stuttgart, who really were a revelation to me. I’d never heard choral singing – if you can call it that – of such beauty. I really wanted to work with them again.

Because I’m working on this opera, I didn’t want to learn a lot of new scores, and so we came up with these two pieces for choir and orchestra, by Boulez and by Ligeti, both of which I’d conducted before, though never together. They also wanted to have a piece of mine, and it seemed obvious to make that Ringed by the Flat Horizon, since the orchestra had performed it all those years before. The Haas was their suggestion, and Winrich Hopp’s, and I was very happy to do it, because it’s a very spectacular piece – extraordinarily spectacular, with its six pianos in different tunings.

No, I haven’t.

Is it? (Pause.) Yes, but Messiaen had started writing his opera long before my piece, so I have to claim for him complete innocence, complete innocence. However, I remember that when I played the piece for him the first time, he looked at one of the chords in the latter part of it, and said: ‘But it’s only in fourths, and yet it doesn’t sound that way.’ Now there are some chords in fourths in the opera, with very few notes, associated with St Francis himself, but again he must have written them already, and it’s just a coincidence.

Well, it doesn’t seem like going back after all that time, because I’ve conducted it every couple of years. But yes, it’s not the way I write music now or would want to write music now. It’s very hard for me to connect to it now, compositionally. But as a performer, yes, I enjoy doing it.

There are things I might have done better, in formal terms, and also having to do with the medium-background material, which isn’t so much what interests me now. All the same, it’s done. And maybe it works, so let’s leave it that way.

I was eighteen to nineteen when I wrote it, so it was a very big experience for me. It was my first piece for a large orchestra. Also, the writing of it was very intense, and stretched over a long period. I started to write it in early 1978 – perhaps even before that; I can’t remember – and gave up, and wrote some other things. Then I went back to it and worked very intensively for ten months, which for a person under twenty is quite a large proportion of your life.

Of course, I’d been to many, many orchestral concerts already, and picked up a lot about the orchestra, and loved the orchestra.

Yes, because of the resources involved. I’ve only done that twice before, including just recently at the Concertgebouw. You need very fine choral singing, just from women’s voices, and the piece has an extremely eccentric orchestra, with no violins, very few other strings, but ten flutes and clarinets. It needs a quite particular stage setting, and so is not easy to put on at all. But it’s such a beautiful piece. Of course, there are a lot of beautiful pieces by Ligeti, but in some ways this is his most beautiful. There’s a point, about eight or nine minutes in, where the harmony just blossoms. A bass line has been holding a tritone, B–F, for about five minutes, literally, and then out of the blue it shifts down a perfect fifth, which in the 1970s, with octaves, was a somewhat forbidden fruit. It’s just so beautiful – so beautiful that afterwards I think he felt a bit guilty about having written it.

Both these pieces, the Boulez and the Ligeti, come from the beginning of the 1970s, and they’re both skyscapes, or landscapes, with drones and female voices, very beautiful, made out of mixtures of instruments and voices – and they’re both rather zen. The Boulez in its first past is more scattered, more abrupt, but it settles into this fantastically calm, serene atmosphere with artificial bird songs. It’s a piece I’ve done often, as often as I’ve done anything; I did the British première of the revised version. It’s just one of those perfect things – as perfect as anything he’s ever done – and it’s very close to my heart. It’s not easy to perform; it’s very supple, with a lot of changes of time and feeling and direction.

So here we have these two major figures, Ligeti and Boulez, both represented by such beautiful pieces, and I thought it would be nice to bring them together.

No. He gave me a lot of useful things about conducting Éclat/Multiples, which is unbelievably hard to conduct, and Mémoriale, but I don’t think we talked about this piece.

I’m not a great expert on his music; I know only a few pieces. But his work interests me. The orchestra knows this piece very well, because they gave the first performance and have played it many times.

I think so, yes.

It doesn’t quite work like that…. But the harmony is very inventive, and I’m looking forward to seeing how it works. The whole piece is one of those extreme ideas.

I have four days, with four and a half hours each day. My own piece I can put together in a couple of hours, and the orchestra is, of course, familiar with Boulez’s music, which in this case is not terribly hard. Then, as I say, they know the Haas, which we’ll have one whole day for in Munich, because I don’t think you could get six pianos on the Freiburg stage.

Yes, which is a lovely place – it’s where Written on Skin had its German première. I’ve also conducted at the Herkulessaal, which has a fantastic acoustic but is a terrifying object.

Because of the Siemens Foundation support.

Well, I’ve conducted for musica viva before – that was at the Herkulessaal – and the place was absolutely full, for a programme consisting of Ligeti’s Lontano, Messiaen’s Réveil des oiseaux, the world première of Tristan Murail’s piano concerto, and my own Palimpsests. It’s a wonderful audience in Munich, totally silent and receptive. I think this is one of those places – Basel is another – where there is a strong audience for contemporary music.