Frank Gehry's Pavilion is now fully erect - and will be serenaded into a state of openness by Thomas Adès tomorrow night.

The eminent composer will perform his own works at the piano, and conduct a small ensemble through Steve Reich's New York Counterpoint and pieces by Stravinsky. The performance will be accompanied by visuals from the video artist Tal Rosner. Adès and Rosner (his partner) are making a habit of inaugurating public spaces, having done a similar job at the Festival Hall in 2006.

Once the music's over, Gehry's Pavilion will remain outside the Serpentine Gallery until 19 October, making it, for four months only, the only edifice in London designed by the man often dubbed the world's greatest architect.

It continues the Serpentine's honourable tradition of commissioning quirky works from the world's top architects, such as Rem Koolhas's balloon-like "tethered testicle" of 2006 and Daniel Libeskind's asymmetric shards of 2001. Gehry is responsible for the undulating expanses of the Walt Disney Concert Hall in Los Angeles (where the architect first met Ades) and the Guggenheim Museum in Bilbao. For London, he has made a rickety pile of chips impaled on spikes.

So what's it for? For the fun of it, mostly - and to serve as a cool venue for the star-studded Serpentine Summer Party on 9 September.

But the Pavilion will also serve some purpose for you and me as the main site of the Serpentine's annual summer events programme, Park Nights, which includes a number of talks, screening and concerts. Next Friday, international star architects such as Daniel Bosia and Sou Fujimoto will discuss the role of revolutionary architecture; the week after, the great philosopher John Gray will read and chat with the novelist Hari Kunzru.

Later in the summer there will be free film screenings on a 50ft screen by the Serpentine lake itself. Programmed by the artist Richard Prince - the subject of the gallery's current exhibition - the season includes the cult road movie Two-Lane Blacktop (15 August) and the classic film noir The Honeymoon Killers (16 August).

The Pavilion is open from Sunday daily 10am-6pm, Fridays 10am-10pm, and is free. Events are ticketed: 020 7402 6075. www.serpentinegallery.org.