Robert and Maria @ Nottdance

Ever since Brecht banged on about the fourth wall - or perhaps when Aeschylus' chorus first entered and sung to the amphitheatre - the relationship between the audience and performer has been debated. The enthusiasm for You Me Bum Bum Train comes from a fascination with the sheer immersiveness of the production, and even a less controversial show, like Hotel Medea, can pose complex questions about who is the actor and who is the observer.

The nineteenth century ideal of the artist is still common. The great individual makes their art and reveals their wisdom. The audience gets to admire it, or hate it, and their role is merely to be a witness to the art. Add in the spice of modern consumerism, and the audience is merely a passive receptacle for the genius's seed.

What the contemporary trend for immersive theatre suggests is that the audience has more responsibility for the creative process. Ontroerend Goed make a point of including their response in their performances. The belief that art takes place at a point of connection between audience and artist is more than a fanciful version of the Sistine Chapel's vision of Man and God touching. It is a vibrant tool for devising theatre.

Both Robert and Maria and Assembly (part of Dance4's Nottdance 2013) rely on this moment. While Robert and Maria provides tiny details, the most dramatic moments happen in the imagination of the audience as they try to make narratives to explain their meaning. Assembly is more literal, adjusting the number of dancers to audience members, and moving from one scene to the next on cues from the entry of new audience members.

Since Nottdance is based on a cheeky pun, it is unsurprising that Assembly and Robert and Maria take place at the very edges of what can be considered dance. Their interest in abstract movements that imply narratives but are applicable to multiple interpretations line them up with most contemporary dance - for all Martha Graham's efforts, choreography is not as precise a medium as verbal language. Yet the more expected distinctive features of dance - the technical skill, the choreographic vocabulary, the precision of movement - are absent.

Any festival concerned with experimental art is likely to have works like these, however, because it is the relationship between audience and performer that the most difficult questions of format are being asked. Debates about "what is dance?" have been largely fruitless since choreographers like Pina Bausch insisted on having doses of chat between the physical work-outs and slapping lapels onto performances is fun, but speaks nothing of the emotional impact of theatre. Questioning the assumed positions of audience and actor,  on the other hand, cuts to a fundamental characteristic of theatre.

If all that  Robert and Maria or Assembly had to say was in the  exposure of this relationship, they would be empty pieces: rather, they use the challenge of breaking the expected relationship to open up the ideas within their pieces. Robert and Maria offer a contemplation on  devotion: Assembly plays out the impact of new members joining a social group. If it can be difficult for the audience to accept their new role as co-creators, this strategy has the virtue of helping theatre become a more inclusive, and flexible, art.