Bach’s final work The Art of Fugue, left incomplete at his death in 1750, has long been famous for (among other things) not having specified its instrumentation. It’s written in open score – each line of music, or “voice”, is given a distinct printed line, making it hard to guess what instrument Bach actually had in mind to play it. The work’s exceptionally complex counterpoint led many musicologists to assume, in fact, that it was primarily intended as a sort of study guide rather than something to be performed.

However, research in the mid 20th century led the Bach scholar Gustav Leonhardt to argue persuasively that it was intended to be performed on a harpsichord: the open-score layout is actually not exceptional for such compositions, and further, the mere fact that it is possible to play this monumentally involved work on a keyboard is likely to be more than mere coincidence. But the two centuries of uncertainty regarding the work’s instrumentation continues to exert its influence today: it has led to a wonderfully rich history of arrangements and transcriptions which shows no sign of abating. It’s been recorded by orchestras, wind ensembles, brass ensembles, electronics, and many other unlikely combinations – all of which make Fretwork’s version for four viols, presented in concert at Kings Place last Wednesday – seem relatively conventional.

That’s not to say that it isn’t beautiful: the precise, serious tone of the viols is a wonderful analogue for the nature of the piece overall. And what’s more, this sort of arrangement has one key advantage over performances on keyboard instruments, in that each line of counterpoint can be heard on its own, without getting lost in the texture, as can happen when all parts are performed together on a single instrument.

The amazing musicality of Fretwork, moreover, means that it’s hard to imagine a more graceful rendition of The Art of Fugue than this. The concert consisted solely of their performance of the first eleven of the completed fugues and then the incomplete no. 14, stopping politely at the point where Bach’s score drops off. Their sharp characterisation of each fugue ensured a slightly more varied evening of music than this might have been, and their thoughtful reordering of the sequence also contributed to a subtly different perspective, teasing out the occasional similarity or difference between pairs of fugues not usually heard adjacently.

But that said, I felt that we could have expected a little more from this event, which after all was part of a concert series entitled Bach Unwrapped: it’s hard to see how such a straight presentation of The Art of Fugue, with no word of explanation from the stage and no additional music in the programme, could have been expected to “unwrap” or explicate any aspect of Bach. The work is so totally shrouded in mystery, in fact, that it is perhaps this, among all of the composer’s vast output, that most needs a careful contextualisation when performed in the concert hall.

With its dense texture and uncompromisingly academic nature, The Art of Fugue makes the vast majority of contemporary music sound like easy listening. It’s also – by its very nature, if no completion of the final fugue is performed – an unsatisfying experience. I wouldn’t criticise the brilliance of Bach’s writing, of course – nor Fretwork’s credentials – but as a concert experience this needed something more.