Ok, I finally got the full scoop on the new Mediastation Vocalist. And here it is:

Ensnareyou, you will be pleased to know it is extremely similar to the software processing for the pitch shift and time stretching features of the Mediastation, it is actually designed by the same developers

The engine that drives the Vocalist is called meloscaline. It contains Elastique, the same engine that drives the pitch shift/time stretch function. Here is a quote from their website: http://www.zplane.de/showPage.php?SPRACHE=UK&PAGE=products17

description
meloscaline is the world's first intelligent harmonizer featuring integrated voice leading rules. The original key, tuning frequency and pitches of the input melody is detected automatically in order to generate harmony voices and/or map it to another scale.
Furthermore, meloscaline transforms any recorded melody from one scale into another.
In contrast to existing technologies meloscaline choiralizer does real voice leading. The intervals of the accompanying voices are not fixed but rather chosen according to voice leading rules and the underlying harmony. meloscaline allows high quality formant preserving transposition and scale conversion, i.e. the characteristics of the original singer or instrument are maintained

technology
meloscaline choiralizer integrates sophisticated harmonic modeling and voice leading technology to generate the optimal harmonization of the input. For each input pitch, the best harmony as well as the best progression of the synthesized voices is computed, resulting in a perfect sounding hamonization (see figure).



As a technology demonstration, meloscaline illustrates the musical possibilities of the combination of various musical analysis and synthesis technologies that are offered by zplane. For the detection of the key and the standard pitch [tONaRT] is being used, while �lastique SOLOIST V2.0 executes the actual transformation and voice synthesis.

More info is available on their website: http://www.zplane.de/showPage.php?SPRACHE=UK&PAGE=products17