Imagine a traditional classical music concert and at the centre of it all – like a spider in its web – is the conductor. He's probably male, although that's changing – slowly – and he's probably in white tie and tails, although that's changing too. He may have a baton (or even a toothpick) or he may sculpt the music with his hands. What happens when you remove the conductor from this picture? And how vital is the conductor anyway? At Paris' Salle des concerts – the Philharmonie's second hall – Les Dissonances provided some of the answers.

Chamber orchestras sometimes perform under the direction of their first violinist – starry ones in the case of Joshua Bell and the Academy of St Martin in the Fields – but a symphony orchestra? Les Dissonances describes itself as an “artistic collective” and the first symphony orchestra to play without a conductor, where “all musicians are equal”. It plays under the artistic direction of David Grimal, who takes what is traditionally the leader's chair, and they rehearse “in a casual context where each member is given the freedom to create their own role”. Aspirational – and inspirational – rhetoric.

Debussy 100 is another of the Philharmonie's imaginatively planned themed weekends involving several ensembles. Les Dissonances' programme was entitled ¡Viva España! placing Debussy's Ibéria (from Images) in the context of other French impressions of Spain by Ravel and Lalo. There is plenty of colour in these scores and Les Dissonances exploited a full palette in bright, sometimes brash, brushstrokes.

Playing without a leader meant different members providing upbeats, so the second violinist launched Ravel's Pavane pour une infante défunte, while in Lalo's Symphonie espagnole – in which Grimal was the violin soloist – flute, harp and brass also had responsibilities for kicking off certain movements. Apart from a soporifically paced Pavane, most tempi were judiciously chosen, but problems arose around ensemble cohesion and dynamics. Les Dissonaces made a big, punchy impact in the small hall, which suited Lalo's concerto-in-all-but-name very well, but was more problematic in Ibéria, where subtler shading is required. There were moments when the presence of a conductor would have ironed out messy cello pizzicatos in the Alborada del gracioso or tightened up the rather meandering route and tempo fluctuations taken in “Par les rues et par les chemins” of Ibéria.

But the orchestra's ebullient spirit won the day, powered by Grimal's charismatic presence. His violin tone in the Lalo – luscious in the lower register, nutty sweetness at the top – charmed and his “leading” in the second half of the concert was characterised by the raising of his right foot for dramatic effect in the guitar-strummed pizzicatos in Ibéria's festive finale. This is an orchestra of big personalities – the clarinet waved his bell in the air for his declamations in “Le matin d'un jour de fête” and the timpanist – who swapped to celesta during the Debussy – attacked the close of the Alborada with brio. In short, Les Dissonances is an orchestra that appears to have a lot of fun and its spirited playing is infectious.