With the Freesound API you can browse, search, and retrieve information about Freesound users, packs, and the sounds themselves of course. You can find similar sounds to a given target (based on content analysis) and retrieve automatically extracted features from audio files, as well as perform advanced queries combining content analysis features and other metadata (tags, etc...). With the Freesound API, you can also upload, comment, rate and bookmark sounds!
In order to use the Freesound API you need to be authenticated with an API key. You can manage your existing API keys or apply for a new one in the following url http://freesound.org/apiv2/apply (Freesound login is required).
Freesound is an open-source project and we will be very happy to get more people involved in its development! We coordinate using a Github public repository to host the code, organize the work to do and discuss about specific implementation aspects. Furthermore, we also have a google group to discuss about more general ideas and future directions of Freesound (http://groups.google.com/group/freesound-dev). If you want to contribute, don't hesitate to contact us!