After the controversial gala to launch the restored Festival Hall organ, comes the serious and enjoyable business of hearing the instrument in multiple contexts, and the first of Yannick Nézet-Séguin's two concerts with the London Philharmonic was structured around two major works for organ and orchestra: Poulenc's 1938 Organ Concerto and Saint‑Saëns's Organ Symphony of 1886.

They serve very different purposes. Poulenc looks quizzically at the organ's role in church and fairground music, before closing in awed admiration of the instrument's potential to convey the intimacy of private spiritual feeling. Saint-Saëns uses it to add majesty and range to already complex orchestral textures and symphonic logic.

James O'Donnell was the organist in both works, underpinning Nézet-Séguin's lean account of the Saint-Saëns with penumbral drones and slowly evolving chords before launching the finale with floor-rattling power. It is Poulenc, of course, who gives us the greater idea of the organ's tone colour, and the results were unfailingly exciting. The score, not O'Donnell or Nézet-Séguin, was responsible for the occasional blurring of orchestral detail beneath the soloist's decibels. The central work, meanwhile, was Berlioz's song cycle Les Nuits d'Eté, orchestrally perfect, though sung underwhelmingly by Sarah Connolly.

Two days later, Nézet-Séguin conducted Mendelssohn's First Piano Concerto and Mahler's Ninth Symphony – the performances in both (organ-less) works proved imperfect yet engrossing. Nicholas Angelich was the soloist in the Mendelssohn, realised on a grand scale but with terrific panache. Mahler's great confrontation with mortality got off to an uncertain start with a shapeless account of the opening andante. Things rapidly improved thereafter. The bitter ironies of the central movements were immaculately judged; the finale, consolatory rather than bleak, was extraordinarily beautiful.