Title ET - Extended Trombone, making music with sound libraries Abstract Are search engines musical? Can we use them in combination with sound libraries as a direct route to creating sonic structures? Is it possible to perform a sound library? Sound library and categorisation systems are essential tools in sound design and computer-based composition. Categorised thinking about sound in order to create compositional structures is not a new idea, the work of Edgar Varèse illustrates the potential for “library thinking” well. Conventionally, a library of sounds will be searchable by keywords relating to a particular sound and this is useful for getting the right (or nearly right) sound for a particular task. We have found that search results reveal structures that can be musically useful, especially in improvised and live performance contexts. John Kenny has been developing extended techniques for the trombone across his entire career and we have been working together to develop a sound library of some of these effects. We have been using the library to create live performance structures and have also been experimenting with using live musical input to search the library and display results. Working in this way permits the roles of the two musical agents (performer / computer) to switch responsibility from leader to follower whenever this is required.