First sight of the Proms ... and not a flagwaver around

The vast space of an empty Royal Albert Hall fills with the stirring sounds of a symphony orchestra in full flight.

Centre stage, two small dark-haired women play facing pianos, their heads bent over their keyboards in concentration as they keep pace with the piece's sudden tonal changes.

The Labèque sisters, Katia and Marielle, are in their final rehearsal of Poulenc's Concerto for Two Pianos, their star turn with the BBC Symphony Orchestra at this evening's First Night of the Proms. It opens the 115th season of promenade concerts, the annual two months in which London becomes the centre of the musical world.

Multiple pianos feature in five other Proms and 9 August has been decreed Multiple Pianos Day, on which the Labèques will return alongside two other duos, Philip Moore and Simon Crawford-Phillips, and sisters Lydia and Sanya Biziak. An evening concert features works for up to four pianos.

The Labèques make their third appearance on 17 August when they perform the British premiere of a work written for them by Dutch composer Louis Andriessen, The Hague Hacking.

The sisters, of French-Italian parentage, launched their international career at the 1982 Proms and were based in London between 1986 and 1993.

Before yesterday's rehearsal, Marielle said: "We love performing at the Proms, it's unique." Katia said: "The Royal Albert Hall is so big but it doesn't feel like that on stage, you can hear yourself play." Marielle added: "It is almost a festival atmosphere and you get the great mix of people, but it's indoors and not raining." The critically acclaimed sisters are part of a new breed of classical musicians exploring other genres. They have worked closely with jazz musicians, count Madonna as a fan and have played Ravel's Bolero accompanied by Basque folk musicians.

Eclecticism is a theme of this year's line-up. In addition to British orchestras, it features international stars such as cellist Yo-Yo Ma and conductors Daniel Barenboim and Zubin Mehta, the Ukulele Orchestra of Great Britain and jazz veteran Stan Tracey. It also includes the first Bollywood Prom.

Drum and bass pioneer Clifford Joseph Price, known as Goldie, who came second in the BBC's find-a-conductor reality show, Maestro, was commissioned to write Evolution!, a Darwin-inspired Prom for children on 1 and 2 August.

Among the 100 concerts will be 19 chamber music events at Cadogan Hall and five Proms In The Park around Britain on the last night.

Some highlights of the season

18 July: Haydn: The Creation. A celebration of nature, life and love in the "Enlightenment spirit", aided by three angels

30 July: Berlioz: Benvenuto Cellini — Overture; La Mort de Cléopâtre. Mendelssohn: Symphony No.2, Lobgesang, with soprano Sally Matthews

1 August, repeated 2 August: Evolution!: concert for children inspired by Charles Darwin with CBBC presenters Barney Harwood and Gemma Hunt and special guest Sir David Attenborough — plus work commissioned by Goldie

1 August: 75th birthday bash for MGM film musicals such as Meet Me In St Louis and The Wizard Of Oz. Singers include Kim Criswell and Sir Thomas Allen

22 August: Beethoven's opera Fidelio conducted by Daniel Barenboim with the West-Eastern Divan orchestra of Israeli and Palestinian musicians

6 September: Handel's Messiah, with youth choirs

10 September: Nikolaus Harnoncourt conducts the Vienna Philharmonic

12 September: Hyde Park hosts Proms In The Park, featuring Katherine Jenkins, tenor Gardar Thór Cortes, and Barry Manilow