This paper describes two site-specific musical compositions, focusing on how modelling was used in their respective composition processes. Primarily, the acoustics of the sites were modelled to aid in the preparation and composition of the pieces. From this we propose the general use of modelling as a way to work with the concept of site. But the idea of formulating a model is also applicable more widely in the work described and this is discussed with the two pieces as starting points. Both pieces use acoustic room scale feedback as their only source of sound, so the impact of the room, speakers and microphones used is immense. The first piece, Rundgång, is a commission for the GRM Acousmonium. The second piece, Clockwork, is a public installation that will also be the site of a performance, combining the installation with live interventions. Clockwork will also employ modelling as a component of the piece itself, and include a remote performer and a remote audience. We suggest that there are possibilities to employ compositional strategies to embrace these kinds of hybrid presence situations by composing for many vantage points.