IT IS marvellous what you find behind closed doors on an unsuspecting street in south Edinburgh, where ambulances screech past furniture shops and defunct tanning salons. John Kitchen has five keyboard instruments in his house and not one of them is a normal piano. 1811 square piano, yes, various harpsichords, naturally, even an oak chamber organ with a handsome set of pipes. “The only time I got a complaint from the neighbours was when a few students were round and one guy used the organ to accompany himself on a Spice Girls number,” Kitchen recalls. “The neighbours banged on the wall and told him to shut up, which I thought was fair enough.”

Kitchen is one of Edinburgh’s finest musical treasures: 27 years a senior lecturer at Edinburgh University, 12 years at St Andrew’s University before that, supposedly now retired but in reality anything but. He’s the City of Edinburgh Organist with regular duties at the Usher Hall; University Organist with duties at the McEwan Hall and director of music at Old St Paul’s Episcopal Church. “Oh, and the Friends of St Cecilia’s keep wheeling me out for various occasions,” he adds, admitting that he is “unspeakably excited” about testing out the newly refurbished organ when the 18th-century Cowgate hall reopens in the spring. And for two days this festival, Kitchen is inviting the public into his home for a pair of house concerts.

The photographer has arrived before me and is having great fun taking snaps of Kitchen in front of various instruments – the organ, especially, which looks improbably grand in its position sprawled across the entire back wall of the living room. Once settled into an armchair Kitchen tells me how it all began, how “it was always about the organ” for him. As a boy in Coatbridge he longed to have one at home and eventually (aged seven) got fed up of waiting so gathered some bits of cardboard, propped them up on his mum’s piano and drew circles across them to make something that looked like stops. When he finally (now aged eight) got his hands on a real church organ complete with non-cardboard stops, he began accompanying the other children at Sunday School and has never really looked back. “I just announced one day I could play and they seemed to go with that,” he chuckles.

Kitchen’s house concerts are designed as up-close affairs. Maximum capacity is around 25, give-or-take, with seating including floors and staircases. The programme is designed to show off the character of each instrument. On the petite harpsichord in the front hall – a 1979 instrument made by a Scottish-Italian builder called Lionel Gliori, based on a 17th century single-manual Italian model from Naples – we’ll hear Scarlatti, Merula and Farnaby. On the early 19th-century Clementi square piano made in London, we’ll hear a JC Bach (an arrangement of the Scottish tune ‘The Yellow-Haired Laddie’) and three of Mendelssohn’s Songs without Words.

Head up the stairs and we meet the chunkier instruments. The organ is a local one – built by an East Lothian company called Lammermuir specifically for the Marchmont flat where Kitchen lived previously and where he acknowledges “it did look a teeny bit imposing”. He plays me a few variations by Samuel Scheidt (and no, he’s not beyond a giggle at the name) and the organ makes a pert, warm, rich little sound. “ You see?” he exclaims. “People think of organs and they assume big loud sounds, but it ain’t necessarily so.”

Across the room sits a sizeable harpsichord on which we’ll hear music by Kunhau and Armand-Louis Couperin – it’s a two-manual Dulcken copy of an 18th century Flemish style harpsichord by Keith Hill, to be precise. When Kitchen bought it in the 1980s he commissioned a painter to decorate the inside of the lid. “I asked for loads of camp cherubs and that’s what he gave me… but look here,” he points to one of said cherubs with a cringe. The babe is holding aloft what looks like a flaming e-book reader. “A holy Kindl! It wasn’t quite what I intended.”

The notion of a classical house concert is not new: Kitchen has done them before, and the format dates back centuries. Schubert used to hold informal soirees – gatherings of friends and neighbours with dancing and games as well as serious music. The composer and his friends would read Schiller and Goethe and discuss philosophy late into the night; think traditional ceilidh with impromptu turns between the dances. Felix and Fanny Mendelssohn grew up in a home that hosted bi-weekly concerts on Sunday afternoons – both composers wrote and played for these Sonntagsmusiken, as they were called, so when Kitchen plays Mendelssohn’s Songs without Words it will be situationally authentic.

That said, Kitchen’s living room is not quite Mendelssohns’ 100-capacity estate in what was then the outskirts of Berlin; instead we’ll be seated virtually underneath the instruments he’s playing. Do people listen in a different way than they do in big halls? “I dare say they do!” Kitchen ponders. “It’s all a bit, well, intimate…” And does he find himself playing in a different way? “To be honest, I always feel very relaxed – unless I’m playing Bach.” He glances up at a stern portrait of Johann Sebastian that’s hanging over the big Keith Hill harpsichord. “JS is terribly important, of course, and he simply has to be there, but when I play Bach I always feel like he’s giving me a dirty look.”

And then there’s the aspect of chat, which Kitchen applies liberally whether he’s on stage at the Usher Hall or in his own living room. “It’s simply part of the act!” he declares. “But it’s easier when the audience is right there under my nose. They can probe me on things, make me explain things better.” He pauses. “I suspect this whole house concert thing appeals to me because it fills the space that lecturing took up. And you know what? After nearly 40 years in academia, I quite like doing the chat without having to mark the essays.”

John Kitchen’s second house concert is on Saturday