For each organ in the catalogue, as much information as possible is collected, not just stop lists. This information includes all the technical details possible, including wind pressures, pipe scaling, materials, action, etc. For existing instruments, especially historic ones, this often means gaining access to the organ and taking measurements. This is very time-consuming and it is proving very difficult to find suitably qualified people to do it, especially as, due to lack of funds, the IOF has to rely entirely on volunteer help. For new or recently-built instruments, organ builders themselves are asked to provide the relevant information.

Our policy is to include an organ in the catalogues once we have at least a certain amount of basic information. We rarely get all the information we'd like, but once we have a basic spec we publish it in the hope that further details may become available in the future.

The catalogue is published as an on-line database available over the Internet. Among those expected to find the catalogue of interest and use are: organists, organ builders, organ students, restorers, and musicologists.

The IOF is interested in cataloguing all pipe organs (including theater organs) and is not interested only in historic organs (hopefully, today's new organ will one day be historic). Neither does it pass any sort of judgement as to whether an organ is "good" or "bad" or "interesting" or "boring". We also include organs that have disappeared, for historical interest.