The Nash Ensembles' "Echoes of Romanticism" series at the Wigmore Hall, of which this concert was a part, is not really an exploration of romanticism as such, but rather a charting of the rise and fall of Teutonic music between Mozart and Schoenberg. This is a fascinating story to tell, and this evening provided a particular insight into Richard Strauss – a key and particularly divisive figure in this narrative, his career spanning as it did from the highest high-romanticism to the era's last glorious gasps in the perenially celebrated works of his "Indian Summer" period. Wagner and Mozart, his two musical heroes, were each represented by a work which seemed to have a particular bearing or resonance on the Strauss work presented here in excerpts: his final opera Capriccio.

First came Wagner's Siegfried Idyll, in its original intimate chamber incarnation. And the Nash Ensemble showed that it is much to be preferred, the lissome delicacy of each instrumental line and beautiful timbres of the chamber orchestra providing something quite unlike what we are used to with this composer. Wagner as miniaturist! As always on the rare occasions when it happens, I couldn't help but feel what a treat it is to have a double bass in a chamber setting, too – adding depth and breadth to the sound, allowing the treble instruments to sing even more sweetly, and emancipating the cello from its usual role to allow for some gorgeous baritonal melodies. If the piece doesn't quite sustain formal interest in the way that his operas do, we can still be surprised that Wagner can provide us with this gentle confection, so different from anything else in his mature output.

Then, after conducting the first piece, Paul Watkins returned to the stage as a cellist to perform Mozart's C major String Quintet, K515. Dating from 1787, it was composed squarely between his two operatic masterpieces Le Nozze di Figaro and Don Giovanni. Though almost surprisingly dissimilar from either of these pieces in character or sound, the endless boundary-pushing inspiration of this period of Mozart's work is every bit as evident here as in the operas. Perhaps most remarkable in this piece (not to mention apt) is an almost Straussian penchant for delicious harmonic side-slips into distant keys. In the first two movements, Watkins took the clear lead, cajoling the group from the centre of the ensemble, but gradually first violin Stephanie Gonley and first viola Lawrence Power took the reins, trading melodies with each other, as Mozart played constantly with instrumental groupings and alliances. The fact that every member of the Nash Ensemble is a soloist and artist in their own right is part of what makes them such a pleasure to hear, and if the last degree of immediacy and spontaneity was missing here, this was still playing of a very high order.

Partly a farewell and homage to opera, Strauss' Capriccio is the work in which he reconciles the twin influences of Mozart and Wagner most completely and creates something entirely perfect and new, unmarred by the notespinning and dross that is so often a feature of even his greatest works. Finally shed is the heavy "Wagnerian armour" that he promised to cast off after Die Frau ohne Schatten (in a letter to Hofmannsthal); what remains is a beautifully subtle tapestry of Leitmotiv and orchestral warmth, in places not unlike the Siegfried Idyll. And finally a work in his oeuvre that might fairly be dubbed "Mozartian" in its poise, flawless aural surface, and wit – it is always a grave misunderstanding when this epithet is applied to Der Rosenkavalier, glorious though that opera also is.

We first heard the gorgeous Prelude scored for string sextet, with its obvious echoes of both previously-heard works. The balance here was unfortunately slightly too much in favour of the bass, with the two violinists not quite being able to cut through the densely sonorous lower strings. But this was probably the musical highlight of the evening, the Nash Ensemble players clearly relishing the contrapuntal richness of the score, providing them with endless opportunities for nuance and indulgence.

Then veteran Strauss soprano Felicity Lott, along with other players then joined them on the stage for the opera's final scene, perhaps the greatest of all of Strauss' monologues for soprano. Presented in a reduction by David Matthews especially commissioned in 2005, this chamber-orchestra version saw the six players of the prelude bolstered by a double bass, single winds, two horns, a harp and a harmonium. Unfortunately it lost a great deal in this version, Strauss' magically radiant orchestration here rendered lumpy and glutinous, and Paul Watkins' fairly brisk traversal of the opening Moonlight music (Richard Watkins' ravishing horn playing aside), coupled with problems from the winds regarding ensemble and intonation, meant that it never truly felt settled. Felicity Lott can still turn a phrase, and proved a sensitive interpreter, even if the vibrato is now rather wide and her voice no longer possesses the immense beauty of tone and control of her prime.

An enjoyable evening, then, and some really intelligent programming, but ultimately the music-making was a little too unfocused for it to ever truly take flight.