Hector Zazou and Carlos have worked together many times. When Carlos recorded with “the French Brian Eno” - as someone called him - for one of his albums, he never knew what the final result would be or who he would end up with in the same track, as with Laurie Anderson in this case.
Hector was great at guiding and helping Carlos learn to improvise, not common for Celtic musicians the way that it is in jazz, with the first case of improvisations being more subtle variations, and the second much more obvious.