Prom 52 offered a fascinating musical journey with French organist Thierry Escaich, who juxtaposed the organ music of J.S. Bach with responses to it by Mendelssohn and Brahms, as well his own improvisations on themes by Bach.

Escaich is part of the grand French tradition of organ improvisation which dates back to the 19th century, and he succeeded another great French composer and organist at St Etienne du Mont, Maurice Duruflé. Escaich calls the art of improvisation "composition in real time" and in an interview for BBC Radio 3 explained that he can often improvise for 20 minutes during a Catholic mass "in Bach style, in Romantic style". In discussing Mendelssohn, whose Organ Sonata in A major featured in this programme, Escaich described this music as Bach "with a little more romanticism", and explained that in his own improvisations he adds his own personality to the music of Bach, while honouring Bach's themes, textures and idioms. The end result is music which shines a new light on Bach's original, while demonstrating the exciting range of possibilities offered by this genre.

The organist is a curious figure, even more rarefied than the solo pianist: sitting high up in the organ loft he is distant, removed from the audience (and in a church or cathedral usually invisible). But Thierry Escaich drew the audience into his special sphere with his expansive gestures and obvious engagement with the music. In return, the audience listened attentively, some promenaders lying on the floor of the arena to allow the magnificent sound of the Royal Albert Hall organ to wash over them. Once the biggest organ in the world when it was built in 1871, the Royal Albert Hall organ remains an impressive instrument, its glorious, multi-layered sound filling the entire space.

The concert opened with Bach's Passacaglia and Fugue in C minor, a work built on a 15-note ground bass theme which grows in complexity before bursting into a massive double fugue with the theme as its main subject. The architectural nature of this music, underpinned by great pillars of sound, was given full rein by Escaich, who created a magisterial and symphonic account of this mighty work.

The Brahms which followed was texturally richer but still one felt one had been plunged back into the complex counterpoint of a fantasia by Bach or Buxtehude. Meanwhile, Mendelssohn sat well with the soloist, for he too had a flair for improvisation and his organ music demonstrates his affinity with the stylistic models of the Baroque, in particular the Chorale, which imbues the opening movement of his Third Organ Sonata with its processional episode which gives way to a fugal section. Here the interaction between manuals and pedals is crucial in creating rich contrapuntal lines and this was handled with technical prowess and virtuosic flair by Escaich. The second movement, by contrast marked Andante tranquillo, is a tender hymn, akin to one of Mendelssohn's Song Without Words

Escaich's own Chorale-Études (of which we heard three in this concert) began conventionally enough but soon moved into more expansive territory to explore the full spectrum of the organ's sonic and orchestral range with florid textures, frenetic, urgent rhythms. There were curious rumblings in the lower register interspersed with spooky slices of sound as recognisable fragments of Bach's original were taken away and toyed with, before rising to a dramatic musical denouement. Expert voicing allowed us to fully enjoy this fine instrument's capabilities and Escaich's confident handling of it. Some of Escaich's improvisations had a filmic quality, and in fact he is noted for his "cine-concerts" in which he improvises on both organ and piano for silent films. Escaich's final improvisation was a thrilling journey through a falling figure redolent of Bach, complete with grand trumpet fanfares. This of all the improvisations in the programme truly demonstrated the improviser's art: to take a pre-determined theme or idea as a point of departure and to fully develop it with complete freedom of expression within its constraints without sacrificing flow or energy, or the sense of music being created there and then, thrilling and spontaneous.