The words “Harpsichord” and “Superstar” are not normally placed next to each other, but Mahan Esfahani comes as close as anyone today to meriting that label: performing in the top venues around the world, teaching, commissioning new work and even new instruments. And perhaps that shouldn’t be a surprise, because Esfahani was bitten by the harpsichord bug very, very early.

“I was nine and it was on a cassette tape – remember those? – and I heard Karl Richter with the Munich Bach Orchestra doing Bach Harpsichord Concertos. I couldn't believe that one instrument could make all these sounds, I thought ‘well, it must be four or five instruments’; it was the complexity and the multifarious nature of all the colours of the instrument that really struck me.” When Iona Brown brought the Academy of St Martin-in-the-Fields to Washington DC to play the Bach Brandenburg Concertos, the ten-year old Esfahani nagged his father mercilessly to take him, that it was essential to go to this concert: “I knew from another cassette tape I had that Brandenburg 5 had a big harpsichord solo. And so I saw a harpsichord on stage, and my heart skipped.”

Years and a progression to musical stardom later, that memory, the wonderment of seeing that instrument for the first time (“it’s kind of like a relationship with a person”), is what Esfahani summons up to get him through a rough patch when he is struggling to find the motivation to practise, together with remembering the difficulty of the days before he was able to own an instrument of his own. “I get up in the morning and say ‘hey, your instrument is just in the room next door, so get in there and practise!”

The environment in which Esfahani grew up did not include any idea of a career in the arts. “For a lot of immigrants, there's a kind of view of ‘we're just trying hard to make it’ and being in the arts doesn't necessarily buy that kind of legitimacy or kind of status that being a doctor does, or an engineer – in that sense, we're very similar to American or British Jews. When you're kind of an outsider, you want to have an indispensable position in society and I respect that and over time, I've gained perspective on it. So the artist's life wasn't for us, but I always knew that I wanted to spend my life with the harpsichord somehow. The way I became a harpsichordist professionally was simply that I wanted to spend the maximum time with the instrument.”

Reviews of Esfahani – which he says he no longer reads – mark him out as a highly individual, somewhat unpredictable performer who throws everything at his music. But I’m unable to draw him into describing any particular intent to play in a specific way. Rather, he is conscious of the passage of time: “We change as people, so we change as musicians too. Actually, the way I play reflects the way I’m feeling at the time. Recently, I was going back to the Johann Gottlieb Goldberg Concerto which I first played in 2008 – it was my debut at Wigmore Hall. Now that I’m coming back to it and studying it – oh man, I used to play it so differently! I was very reserved, I was trying to prove myself, I wouldn’t take risks because of the fear of making a small technical error.” On a recent visit to Nimbus Records at their Wyastone Estate, Esfahani was playing through old CDs and discovered that Shura Cherkassky, one of his favourites, changed totally between his 40s and his 70s, “because he was a different person. And you know, Bach wrote differently. What's really interesting is seeing Bach revise his works later in life, because things become more distilled – they become much more simple. When I did my first recording, of the Emanuel Bach Württemberg Sonatas, I was so conservative about ornamentation. And then right after I did the recording, I found an academic paper about ornamentation of the 6th Sonata and it was really wild: it totally changed my view. Sometimes, you just know better later.”

Esfahani is particularly conscious of the passing of time just now, as a result of the death in September of Zuzana Růžičková, his teacher since 2011 and a major influence. He remarks on Růžičková’s fearlessness, on how she always got to the bottom of a piece of music, how she always put in “that last 5%”, how – in spite of being a concentration camp survivor – she considered music to be a matter of life and death. She held a strong belief in some form of Platonic ideal of Bach’s music, the performer’s task being to search through the leaves and the branches to find that ideal. It’s a strongly different performance philosophy, he argues, to believe that the composer had a purpose in every note and that the performer should try to find that purpose, from the approach that “this is how they did this kind of phrase in that period, so this is how you should play it”. That’s a cynical way to solve interpretive problems, contrasting with Růžičková’s view, much in the vein of Talmudic enquiry, that an interpretive problem is not ultimately solvable: you can get close to it but you will never fully solve the problem. “That’s why Christians have heaven and hell, and Jews don’t have that!”

A colleague recently observed that although Esfahani has a strong interest in artists like Růžičková (and Wanda Landowska and Ralph Kirkpatrick before her), he doesn’t sound anything like them. His response was that “she wasn’t that kind of teacher. Christopher Hogwood studied with her, we sound nothing alike”. Her influence was more about imparting a level of maturity: “Young artists feel compelled to fill in all the spaces but older artists have the courage to wait before stating a new phrase and then to state it with conviction”.

Esfahani being a harpsichordist, it’s no surprise that his relationship with Bach is a deep one: he has “spent a long time with Bach, and that’s a worthwhile thing”. The surprise is when he says “I don’t necessarily get Bach more than anyone else. If you sat down with Bach and said ‘your music connects me spiritually’, maybe he’d say ‘no it doesn’t. That wasn’t my intention’. That probably would not be the case, but I can’t know.” But he does see playing Bach’s major works as the culmination of a musician’s life, something that he can’t say about other composers, and he suspects that if he asked a broad swathe of musicians (from all genres, not merely classical or baroque specialists) who was the greatest composer ever, that most would answer “Bach”.

I ask him about his recording of the Goldberg Variations, released to great acclaim last year. “The Goldbergs are such a personal project, because I’ve lived with them for most of my life, either as listener or a performer, or just a musician who’s admired them – so inevitably, the personal history comes into play. Landowska first performed the Goldbergs when she was in her 50s, I think - and she said "I've been practising the Goldbergs for fifty years". He is also starting to refine his depth of understanding by venturing into the unfamiliar territory of improving his visual skills, learning to draw and reading more about art, architecture and visual principles in general.

He is one of a small number of harpsichord players to strongly embrace contemporary music. “My end goal is that it no longer becomes remarkable for a harpsichordist to play contemporary music more so than for any other musician. I don't want to make it a moral issue, but come on! Music is living! That's my hope, that my work will contribute to that.” He’s excited by a lot of the trends that are coming out of Denmark and, has commissioned a new concerto from Ben Sørensen, together with the Bergen Philharmonic and the City of Birmingham Symphony Orchestra; another of his commissions has been to Iranian Anahita Abbasi (“the most exciting contemporary music in the Middle East, Israel included, is coming out of Iran”). He would have loved to commission Harrison Birtwistle, but Birtwistle refused on the plea of being too old to learn a new instrument. Esfahani is, however, quick to point out that he is not the only harpsichordist engaged in promoting new music, lavishing praise on Polish harpsichordist Goska Isphording, who has dedicated her life to new media and new music for the harpsichord. When asked about who is the next big harpsichord talent, he cites Isphording and two Spaniards: Corina Marti, who plays mediaeval music on the clavisimbalum and a variety of other rare instruments, and Ignacio Prego, who is “a very sensitive and thoughtful person and he has a particular affinity with Bach. He excites me a lot, because he's really one of the rare people that whenever I hear him play, I always think I'm a better person after I listen to him. I think that's going to go a long way into winning acolytes for the instrument.”

His latest commission, however, is not for a piece of music but for a new instrument, as yet unnamed but which he dubs “the harpsichord of the future”. It has been built by the Finn Jukka Ollikka, whose Omniwerk, a combination of bowed and plucked stringed instrument, blew Esfahani away when he saw and heard it at BRQ Vantaa in 2014. The new instrument has a carbon fibre composite soundboard and a rare 16 foot stop which imparts a sub-bass register. “It’s based freely on early 18th-century Berlin building, like Mietke for example. Mietke's instruments are amazing, but we don't have any surviving with the 16 foot stop, so this was kind of conjecture.” The instrument is playable now and “it's loud as hell! It'll be able to hold its own in a concert hall with an orchestra”.

The “harpsichord of the future” appeared in concert for the first time in Esfahani's current home town of Prague, in a concert on January 14th dedicated to Růžičková's memory (reviewed here). UK audiences will hear it for the first time at Wigmore Hall on February 9th, in the next instalment of Esfahani’s Bach Series. Now there’s a date to look forward to.