Crossfade Loop Synth is a simple AU instrument - it loads a sample from disk (in AIFF format) and plays it back in the classic sampler way i.e. higher notes get shorter, lower notes longer. It loops the sample using a crossfade (hence the name). The idea is to make it easy to produce smoothly looping pad sounds from pretty much any sample.
The current version is a very early beta, made available now to invite feedback.