All too often, the beautiful polyphonic music of the renaissance is treated as something soothing, as relaxing background music, but listening to it in this way gives only a small part of the picture, for it misses shapes of the individual lines and the clever interplay between them. A trio from the five members of Phantasm Viol Consort set out to make this point at a concert in Durham Castle’s Great Hall last night, with an exploration of composers who took experimental risks in their polyphonic writing. By restricting their programme to three-part pieces Phantasm gave us the opportunity to pay attention the structure of polyphony, whilst accentuating the inventiveness of the some of England’s leading composers of viol music.

The programme was set out chronologically, beginning with the Elizabethans, then taking us through the turmoil of the 17th century to Purcell, and consisted almost entirely of fantasias, the backbone of the viol repertory. The fantasia, an abstract form, based on imitation between the parts, gave composers plenty of room to experiment, and the first example, by Tomkins was typical of the genre, beginning with plangent simplicity and gradually becoming more elaborate. Byrd’s three Fantasias a3 were livelier and had a rhythmic freedom that was made to sound effortlessly fluid by the three players, but, like most of the music in the programme was probably in reality extremely difficult to keep together.

The Fantasies in Three Parts by Gibbons brought music of greater complexity. The imitation between the parts draws the ear in deep, leading the listener from one melodic line to another, but then surprising syncopations, little jolts that feel like a missed heartbeat and shifts in time signature bring you back out of the individual lines to hear the bigger picture. The perfect unanimity between the three players in their imitative phrases was impressive here and heightened the clarity of the polyphony. This music is never a mere mathematical exercise in counterpoint though and despite the relatively small dynamic range of the viol, there was some beautifully expressive playing; there was an enchanting grace and stillness at the end of the first fantasia, and the third began with a gorgeously shaped solo from treble viol player and leader Lawrence Dreyfus.

Instead of performing at one end of the hall, with the audience in rows, the trio placed themselves in front of the splendid fireplace, with their music lit by big old-fashioned wooden standard lamps, with the chairs set out in a broad semicircle around them. This layout put the music firmly into the intimate domestic setting for which it was written, and the musicians were so deeply absorbed that it was as if the audience were invisible. In other contexts this would a criticism, but here it worked – it was as if were granted the ability to peer back in time, unobserved. The complex music demanded unbroken attention by players and audience, and the spell they cast meant that even the inevitable bits of background noise from resident students didn’t really cause any disruption.

Fantasias movements were mixed with stricter dance forms in Matthew Locke’s Flat Consorts No 1 and 2 (so called because of their key signatures) – Locke’s employer Charles II disliked the old fantasy tradition and wanted modern French dances in his viol music, but ever the individual, Locke twists and stretches the dances so that it becomes hard to distinguish them from the intervening fantasia movements. These two suites were capricious and quirky, full of characterful intricacies with lively bass lines underlying the dances.

Locke is relatively unknown today, but in his time he was England’s leading composer and an important influence on the young Henry Purcell, whose three Fantazias of 1680 finished off Phantasm’s journey through English viol trios and represent the culmination of the viol fantasy genre. The texture of these was much richer, and more polished, and instead of making the listener shift between the individual lines and the bigger picture, Purcell’s writing makes it possible to hold onto both elements simultaneously. The clean, pure tones of the three viols, coloured with a little bit of vibrato gave a severe austerity to the slower passages, but there was flamboyant energy and greater openness in the faster passages, compared to the introversion of the earlier pieces on the programme.

Phantasm closed the concert with a piece that was neither English, nor written for viols. The Contrapunctus 8 from J.S. Bach’s The Art of Fugue would have worked better as an encore – although some sloppy editing in the programme suggested that in fact we had been given a truncated version of a longer concert that included more arrangements of Bach’s keyboard music. That said, it was a delight to hear and it gave the three players the chance to show off some nimble fingerwork.