The most memorable performance in the opening days of this year’s Venice Dance Biennale had barely any dance in it at all. Italian choreographer Andrea Salustri’s Invisible is built around movement, but it’s movement of light, air, water and sound waves, with Salustri and co-creator Alice Rende as shadowy figures conducting the elements. They brew up storms like Zeus and Poseidon, with flashing veins of light, sounds of pummelling rain (in fact small drips and bubbles amplified by powerful microphones) and an enormous amount of billowing smoke that ultimately whips itself into a spinning tornado.Conducting the elements … Andrea Salustri in Invisible. Photograph: Cosmin CirsteaSalustri, who won the Italian callout to create a new work for this year’s biennale, is a circus artist and philosophy graduate, and he is also a choreographer – a definition so much wider than one who devises dance. This year marks the 20th dedicated dance festival in Venice (dance was previously seen as part of the theatre or music programmes here until 1999, since when it has been an annual, then biennial, and now annual feature of Venice’s arts bonanza). In a talk to mark this anniversary, current artistic director Wayne McGregor was joined by four former directors to discuss their aims for the event. The question of “what dance is” kept arising as the ongoing line of inquiry, a question “so ordinary that it is still necessary somehow”, said choreographer Marie Chouinard.