In 1970 Lawrence founded the Electronic Music Studio at the Inner London Education Authority's new Cockpit Arts Centre. There he ran several evening and Saturday courses in electronic music. The ethos of the Cockpit promoted the interaction of different art forms, which was one of the reasons that he became involved. Into one of these classes came Eddie Franklin-White, an artist who was running the Visual-Audio workshop at Hornsey College of Art. Eddie became involved with Lawrence in several multi-media performances at the Cockpit including an event called "Sound. Light and Space". This was designed for the Cockpit's theatre with Eddie creating a lighting score and Lawrence a sound score. The idea was that both scores were articulating the same overall structure, but did not necessarily coincide precisely all the time. Rather, there was a series of 'Tableau's' where the two would come together in a pre-defined relationship. Between these points each element would follow a trajectory leading from one Tableau to the next, but each following its own logic. Part of the character of this idea was that, due to the imprecise nature of the available equipment (basic theatre lighting and EMS VCS3s), the precise relationships of the Tableaus needed 'tuning in', and this gradual arrival at the moment of conversion was a crucial element.
The performance was repeated at the ICES 72 Festival at London's Roundhouse, and it was this experience that led to the formation of Hydra. A revised version of the original piece became "Dodman Point". It established the idea that Hydra would not be a fixed ensemble, but rather a forum for collaboration between practitioners of different art forms. Over the years various visual artists, writers and musicians became involved to some extent. Eddie's work at Hornsey produced a rich stream of experimental artists (Rupert Morley's work with polarised light and lasers, and Gillian Olensky's smoke domes are prime examples). Musicians included Per Hartmann and Simon Desorgher. Sound poets, particularly Bob Cobbing were also involved in some performances.
There were some performances of "Dodman Point" at writer Robin Chapman's home in Wandsworth. For these occasions Lawrence created "Duolith", which opened the programme. Both these pieces have the the audience entering an already established situation; in "Dodman Point" the first Tableau, and in "Duolith" an 'endless' first section made of continuously rotating loops of different lengths. Several performances at London's Institute for Contemporary Arts developed these ideas and introduced the use of lasers and projections. There were other performances at the National Poetry Centre and the Birmingham Arts Lab. "Hydrangea" was a collaboration between Lawrence and Bob Cobbing, articulating the word 'hydrangea' over one hour in voice, synthesised sound, light and projections. The piece was revived for the first Electroacoustic Cabaret, and at that time a score was published by Bob Cobbing's Writers Forum and new slides were made by Rupert Morley.
In the late 70s the crucial people began more and more to be involved in other things, but there was one last resurrection of Hydra for a series of concerts and workshops at the Goethe Institute in London as part of their 'The 70s Meet the 20s' programme.. On this occasion Hydra 'regulars' Per Hartmann, Simon Desorgher and Lawrence Casserley were joined by Rolf Gehlhaar and Richard Bernas. For these concerts we created a collaborative piece "Hydraphone" which was commissioned by West German Radio.. For this piece we each suggested several structural models and decided on one from each of us that all would realise. In addition there were a number of voluntary models which we could choose to realise if we wished. The resulting segments were then knitted together to make the finished piece.