What is the MD disc space allocation algorithm?

According to Minidisc Rainbow Book recommendations (a ``remark'', not a mandatory requirement) the virgin space that runs to the end of the disc (if any) is always the first allocated, followed (in ascending disc address order) by the remaining free segments located throughout the disc. Free segments smaller than 6 clusters (one cluster is slightly more than 2 seconds of SP mode stereo) are not allocated until enough adjacent area is freed to make an open space of at least six whole clusters. (Thanks to David Tamkin for this investigation using a Sony MDS-JE520 MD deck.)