The London Haydn Quartet reaches the end of its period-instrument Hyperion Haydn cycle: well, almost – they still have to release Opp 1 and 2. For now, though, if this is an end, no one who loves this glorious music could have hoped for a better finish. There’s something so fresh and so bold about the two quartets of Op 77 that it’s hard to believe they’re the last words of an ailing composer. They really do feel more like the work of a genius who (as Dr Burney said of Op 76) ‘had expended none of his fire before’.

That fire burns powerfully and cleanly in these performances. As throughout this series, the recorded sound (the venue is Potton Hall) is transparent but resonant, with a certain boominess around the cello adding to the sensation that we’re hearing a public performance in a sizeable hall, rather than anything more domestic. At this stage in Haydn’s trajectory, of course, that’s a valid approach, and once again, the more I returned to these performances, the more I found myself warming to their fantasy, their disciplined spontaneity and their cumulative insights.

So while it’s difficult to capture the full playfulness of (say) the march-like opening movement of Op 77 No 1 in an acoustic as spacious as this, the performances gain in depth of tone and dynamic range, allowing the group to pull and stretch phrases at the end of the movement in a way that accentuates the full grandeur of Haydn’s vision. Similarly, in the middle of the first movement of Op 77 No 2, where Haydn’s harmonies suddenly darken and intensify and vast, Romantic shadows fall across the music, it really helps to have that added richness and resonance in the bottom register. Haydn on a cosmic scale: well, why on earth not?

And yet none of it sounds forced. As well as the buoyancy and silvery quality of the LHQ’s vibrato-light playing, there’s a real sense of invention – of making the music afresh – with a questioning, almost improvisatory quality to the great ascending violin solo at the climax of Op 77 No 2’s slow movement. Dotted rhythms have a spirited kick. The players spring away from the earthy bagpipe drones in the finale of Op 77 No 1, and at both the start and finish of the finale of Op 77 No 2 it sounds as if they’re inventing the music on the wing. The final bars feel entirely satisfying and anything but valedictory. Again, that’s as it should be.

Delightfully, the LHQ have included the exquisite one-off Quartet Op 42 as an encore, and the first movement brought my only really serious reservation about this set. Played with impassioned expression at a slow Andante that isn’t remotely innocentemente (Haydn’s marking), it loses much of the terseness and bittersweet wit that gives this miraculous little work its piquancy. With both repeats observed, that first movement comes out longer than the other three combined.

On the other hand – and possibly this was intentional – if you are going straight on to the second disc and The Seven Last Words, it makes an excellent transition to a performance on the most expansive scale. The dark-and-light contrast between ceremonial grandeur and intimate emotion; the pregnant silences; the tender violin phrasing in ‘Mater, ecce filius tuus’ and the epic solemnity and unearthly sheen at the opening of ‘Consummatum est’ – it all adds up to a wholly persuasive case not just for the quartet version of the Words but for a historically informed approach, too. And of course the spacious acoustic and almost orchestral range of tone-colour are entirely appropriate to a work that English audiences (as Richard Wigmore mentions in his excellent booklet note) called ‘Haydn’s Passion’. If you have enjoyed this cycle so far, you will not be disappointed.