This festival's final morning recital boasted very minimal staging: one chair and four music stands. Sitting, for the last time in Edinburgh as a member of the Emerson Quartet, would be cellist David Finckel. Eschewing seats is not the only unusual element in the Emerson String Quartet; they also shun the traditional power structure of fixed first and second violin: Eugene Drucker and Philip Stetzer share leadership.

The latter led in the first half, which opened with Mozart's String Quartet in D, K575. Written in 1789 for Friedrich Wilhelm II, it is the first of Mozart's three 'Prussian' quartets. That the work's dedicatee played the cello is not only clear from the enjoyable cello part but also from the resulting democratic, less top-heavy writing. As pointed out in James Keller's excellent programme note, the quartet avoids extremes, whether of chromaticism or tempo. Three movements are marked Allegretto and, where an Adagio might have been placed, we have an Andante. On the face of it this might seem to invite sameness and boredom. However, Mozart's operatic genius for expressing character through theme wins the day. The Emerson Quartet's finely nuanced performance was a masterclass in elegance, balance and ensemble. The apparent effortlessness draws upon their 36-year relationship.

It's not difficult to imagine that a piece called Four Quarters, commissioned by a quartet named after Ralph Waldo Emerson, might be somehow relate to T.S. Eliot's Four Quartets. Each movement of Thomas Adès' work represents a time of day, such as 'Nightfalls' or 'Morning Dew'. However, it was the title of the final movement, 'The Twenty-Fifth Hour', which prompted my speculation. Could Adès be alluding to Eliot's metaphysical work and to 'time outside time'? Certainly this movement is temporally complex. The time signature of 25/16 and the asymmetric groupings of fours and threes are intended to remove pulse and, pretty soon, one gives up counting and goes with the flow. This, however, is clearly not possible for the players, as the tapping foot of violist Laurence Dutton attested. This is very much a work of contrasting moods. There is more activity going on in 'Nightfalls' than one might hope for in a nocturnal setting, resulting in a slight unease. The almost completely pizzicato 'Serenade: Morning Dew' also has an edge but ends with a much more light-hearted feel. That was certainly true of this performance, which ended with a physical flourish. The most obviously temporal movement was 'Days', in which the irregular pulsing of the second violin (in threes and twos) confers a sense of measurable pace. I really enjoyed this performance and was intrigued by the piece. I look forward to another hearing. Perhaps the quartet will record it before David Finckel hands over to Paul Watkins.

Following the interval, Eugene Drucker led in Beethoven's String Quartet in E flat, Op. 127. The opening chord was sufficiently long to sense the darkness of the key, contrasting strongly with Mozart's D major. I'm not sure why, but without thinking I had formed the impression that the Beethoven was programmed to contrast with the Mozart and not the Adès. One common feature between the programme's outer works was the prominence of the cello, for the reason that it was the patron's chosen instrument, in this case Prince Nikolas Galitzin.

This was a supremely lyrical performance, with the obvious exception of the Scherzo, which was delivered with a jaunty crispness. The searching quality often associated with late Beethoven was certainly present in the Adagio ma non troppo e molto cantabile, during which the 900-strong audience seemed transfixed. Their response at the end of the Finale was such that the Queen's Hall felt moved to post a video of audience reaction alone on Facebook.

There seemed little doubt that at least a short encore would ensue. And who better to turn to for brevity than Webern. The fourth movement of his Five Movements for String Quartet provided what Philip Stetzer referred to as 'something wonderfully strange'. This quiet piece, shimmering with harmonics, was the polar opposite of the knees-up one might expect of an encore, and it seemed to delight those around me. A chorus of sighs of appreciation could be heard before the applause resumed.