It takes a great orchestra playing at its most effortlessly revealing to show just how complex some composers are.

At the latest in the St David’s Hall international series of concerts, conductor Sir Andrew Davis brought the best out of an already outstanding one in music for which he has a special affinity.

The result was the most surpassing symphonic sounds to have been heard in Cardiff for a long time as music was bathed in glowing light by a band of musicians at full complement..

The originality of Mozart’s Piano Concerto No 9 in E flat is taken for granted yet its autobiographical weight, especially in the central plunge from major to minor, reflects a composer temporarily at odds with his world but burying the difficulties in music of transcendental grace and exuberance.

Lise de la Salle, the young French pianist, was its robust and fastidious soloist, gaining much from the way the orchestra deferred to the keyboard while playing an exemplary role beyond it.

It was in English music that Davis and his players excelled, first in Elgar’s concert overture In the South, then pre-eminently in Vaughan Williams’ London Symphony, both concerned with deeply personal utterance as much as wide-eyed scene painting.

The descriptive passages in both were seamlessly woven while the case was made for their human dimension, indicated by sheer length in the overture as a vehicle for meditation and by swinging contrast of mood in the symphony as testimony to a troubled metropolitan soul.