Wilton's Music Hall in London describes itself as "the city's hidden stage", and rightly so. Nestled in a tiny alleyway in an otherwise dull part of the East End, it's very easy to miss, especially given its outward, derelict appearance. "Niche, arty, folksy, quirky", as I wrote in my notes, really doesn't cover it.

The aforementioned stage is truly hidden for now, as the main music hall is being refurbished as part of a major capital project to restore and improve the building. Wilton's is keeping the front portion of the building open and putting on a series of events in its smaller rooms (the so-called 'constructionism salons'), including an intriguing series entitled Soundbox, in which the violinist Peter Sheppard Skærved and guests present music in a new and informal light.

Informal was certainly the word for the first performance in the series, "New Mysteries – Heinrich Biber Now". Picture an upstairs room, all wooden beams, creaky floorboards and exposed brickwork, and a couple of rows of mismatched chairs. You're encouraged to buy a drink downstairs and take it up with you to enjoy during the presentation – so more of a gig vibe than anything else.

Ironically, it was Biber's pious Rosary Sonatas for violin and continuo that were the focus of the performance. The 15 sonatas correspond to the Rosary Mysteries, with a closing passacaglia believed to represent the Guardian Angels. Sheppard Skærved invited his audience to approach the Sonatas as one might Plato's Symposium – to question what they are really about. On the one hand, Biber used the sort of extended techniques that one might expect to find in the most avant-garde of pieces, with which he could display his virtuosic talent; on the other, he used them for practical and symbolic purposes.

The most obvious of these was Biber's use of scordatura, or de-tuning. A complete performance of the sonatas would have required 14 different tunings of the strings. In practice, Biber's use of scordatura allows for chords and runs to be bowed that would be impossible using the ordinary tuning, and the manipulation of the violin's tone colour to reflect the overall characters of the Joyful, Sorrowful and Glorious Mysteries. Symbolically, meanwhile, the first sonata ("The Annunciation") and final passacaglia both use the standard G-D-A-E tuning, to represent the completion of the cycle, whilst the remaining tunings were all within the range of the standard. The sixth sonata, representing Christ's anguish in his supplications on the Mount of Olives, uses the discordant tuning of A♭-E♭-G-D. Most interesting of all was the crossing over of the middle strings in the 11th sonata ('The Resurrection'). Not only did this allow tuning in perfect octaves (G-G¹-D-D¹) to represent the final perfection in Christ's rising, but the strings' crossing over provided a visual symbol of the sonata's subject matter.

Whilst scordatura was the one technique pervading the Rosary Sonatas, Sheppard Skærved used a well-chosen selection of the individual sonatas to demonstrate the impressive breadth of symbolic and practical approaches contained in the work, from the stretching of strings to represent Christ's body on the Cross to the cantus firmus of "The Resurrection", rather appropriately based on the Easter chant of Resurrexit Christus hodie. The cantus firmus flipped between violin and continuo, allowing bassist Rachel Meerloo to step into the limelight. Sheppard Skærved's use of two violins, including a Stradivarius, and different bows, gave additional insight into the range of tones that might be used to paint each sonata's picture.

As a sort of side dish, the Biber sonatas were interspersed with a contemporary fairytale and modern-day music, each in their own way demonstrating a connection with Biber's school of thought. The Lady of the Rock, a wonderfully crafted story written by Malene Skærved in the Hans Christian Andersen tradition, shared the element of human nature and its fallibility. A "Brautmarsch" from the Hardanger folk tradition shared the use of scordatura. It would have been good to see Sheppard Skærved really getting into his element and indulging in a bit of foot-stomping (which he indeed did in the post-concert chat!), but his playing certainly evoked images of hardy Norwegians doing so. Biber's sonata structures and instrumental techniques were evidently strong influences in a short piece by modern-day composer Sadie Harrison.

Post-performance, the audience was invited to converse with the artists, enabling an even greater understanding of the music. It was fascinating and mind-boggling to go behind the music stand and discover how Biber's scordatura was notated, the notes on the page corresponding to the positioning of the fingers and not the playing pitch.

It is hard to compare this performance with any other – never before have I heard such music in such a peculiar setting. One thing is certain, however: it worked. Now that I know where to find that most elusive of venues, there might even be time to get the drinks in beforehand!

New Mysteries - Heinrich Biber Now, at Wilton's Music HallJulia Savage reviews Soundbox 1 at Wilton's Music Hall, with Peter Sheppard Skærved.4