Presumably utils 0.5.10 and libs 0.5.10b work ok with 0.5.12a. The alsa home page at http://alsa-project.org/
confirms that these are the last 0.5 releases.
The important thing to realise about Alsa is, that (quote from web site) -- "*** N.B. The 0.5.x series is considered deprecated and is no longer supported by ALSA developers *** ---.
the 0.9 series is infact very stable and actively supported. (even tho it is labelled as a development release.) The release candidate of 0.9 is now available.