You do seem more willing than many of your colleagues to take these compositional risks - adding music where it missing, mixing your own compositional efforts with Bach’s music.

When I went to conservatory in Holland, I wanted to study composition as well, but I always composed in 17th or 18th century style. The teacher at the conservatory felt that I should change, that I should write in a modern style. I said to him, “but I’m not interested in doing that”, and he replied, “then I’m not interested in teaching you”. So occasions like the ones I just described - and others like composing cadenzas for soloists - are welcome opportunities for me to write my own compositions (or just additions) in a style I like without feeling guilty about it. A good example is my reconstruction of the St Mark Passion, where I composed the missing recitatives, and at the moment I am working on a similar project, reconstructing Cantata BWV 205a - my first version is ready. We’re going to perform that in Dresden, it’s not for a recording. There are major problems, nothing is 100% clear. Musicologists have made suggestions on how things should go; but BWV 205a is lost, and I think it is impossible to reconstruct it as Bach performed it. Some of the arias and the choruses have survived, but you have to find other solutions for the missing arias. I like to tackle these problems with a fresh view, trying to find my own solutions, and so I did. It’s a puzzle to find out how at some point the text will fit. How practical was Bach with his parodies? We still know too little about this.

In BWV 205a I had to compose the recitatives - that goes quicker and quicker now, as I’ve done quite a bit of this by now. All such projects add to the joy of working on the Bach cantatas, and give me the opportunity to feel, in several ways, like a student of Bach’s.

Do you listen to other peoples’ recordings?

Not really. In the beginning, I did exchange CDs with Masaaki, and I got one CD of Gardiner’s Pilgrimage as a present. But I think that, in the end, you should do what you think It doesn’t help to compare yourself to others and do something just because nobody else did it. It’s good to know what colleagues are doing, because sometimes there could be fantastic new ideas as well, but you should be careful - you should understand why they did what they did and decide for yourself whether their ideas are convincing.

Sometimes it is interesting check to see what other people do with, for example, the transpositions in the early cantatas. The bad thing in the early music world today is when somebody does something, and other people take it for granted and do the same unquestioningly.

You might be familiar with the idea that what is usually described as historical performance is actually a reflection of 20th century aesthetics, with historical research only playing a small part. This view was especially promoted by Richard Taruskin [Text and Act, Cambridge University Press, 1995], who argues that historical performers should actually take pride in this - that being a representative of your own time is better, indeed more authentic, than being an archaeologist.

But I’m convinced that research is very important. I wouldn’t be the musician I am now if I hadn’t done that, and I’m still reading as much as I can. I cannot deny that I am Ton Koopman - my own personality affects how I perform music, but then the same was true of Baroque musicians. If Handel were to play one of Bach’s pieces, or vice versa, perhaps their performances of each other’s music would not have been entirely ‘authentic’. The best we can hope for today is to try to be like students of these composers. This does not mean giving up your own personality. Bach’s own students were not all the same. There were real antipodes among them - think of Müthel and Johann Christian Bach, or Kirnberger and Wilhelm Friedemann Bach. But they all knew the language of the time, and they were all recognisably students of Bach. When I consider this, I think we have a chance to play more authentically than people sometimes dare to believe. We can learn the language of the time. Of course, we cannot escape the influences of our own time as well and I’m certain that pop and jazz music have had some influence on the way we shape Baroque rhythms - even in my case. I don’t like pop music, but I have heard it and my father was a jazz musician, so that has certainly influenced me. But our desire to make these rhythms lively is historically informed. Everybody danced in the 18th century as well. I’m not actually certain, given the Lutheran atmosphere he grew up in, whether Bach himself ever danced.

Of course, we cannot escape the influences of our own time as well and I’m certain that pop and jazz music have had some influence on the way we shape Baroque rhythms - even in my case. I don’t like pop music, but I have heard it and my father was a jazz musician, so that has certainly influenced me.

Although I danced a few times, I never enjoyed it. But dance and its rhythms are still very central to Bach’s music, and it’s an element I enjoy and which I like to bring out.