In March 2011, AppleInsider was first to report that Apple would be bundling dozens of high quality new speech synthesis voices supporting a wide variety of languages and regional dialects.
Mac OS X Lion shipped later that year with support for downloading the optional voices within the Speech pref pane of System Preferences. In Mountain Lion, OS X retains the default system voice of Alex, first introduced in OS X 10.5 Leopard in late 2007.
However, uses can browse higher quality alternatives (pictured above) from the revamped Dictation & Speech pref panel, by selecting "Customize" from the System Voice selection popup.
The system will then download each of the selected voice packs chosen for installation by the user. The optional voices weigh in nearly 1 GB each.
Shortly after the release of Mountain Lion on Wednesday, Apple made available a series of "2.0" Voice Updates for each of the optional voices users had previously installed. Each update "delivers pronunciation and clarity improvements."