Mozart is a genius when it comes to letting the music convey the meaning of the words and vice-versa. I think it's more than just the style of his vocal compositions. I'd imagine this is hard to write about unless you know Mozart's vocal compositions, including Lieder, opera arias, concert arias, religious music etc.

It's much more than "the style of his vocal works"- this would mean only the composition, but it has to do with the combination of both. It has nothing at all to do with recording!!!

...is backed by an amazing one google hit! A rather classy reference though: Somewhere insinde the "Proceedings of the Royal Musical Association", 25th Session 1898/1899 it reads
"They must have felt that this was as much a new creation demanding genius to conceive as any musical setting of language" (Joseph Goddard: The Philosophy of the Higher Beauty of Music).
Hope it makes you wiser. I reckon this suggestion doesn't require a great of creativity to come up with after Diana's answer, but I feel that "language" should be used rather than "words" because it's not simply about finding the right notes for a number of single words and lining them up, but about setting patterns which emerge on a higher level than that of single words like the intonation of sentences. These patterns are more than the sum of their parts, and while "words" can mean more than a bunch of randomly sorted flashcards, "language" clearly does mean greater patterns. After all, the author chose to write "Sprachvertonung" rather than "Wortvertonung".

Scientists of the University discussed (the) fundamental features of the musical setting of language in Mozart's vocal oeuvre.

Scientists of the University discussed (the) fundamental features of Mozart's setting of language in his vocal oeuvre.

Notes (without relevance to the question): I can't tell whether to use the article here because there is a mistake in the German sentence (word missing/wrong case).
As for the "fundamentalen Aspekte", maybe I have just a too imaginative way of understanding words, but I find the idea of an aspect of an object, i. e. of a way of looking at the object, as being fundamental for the object odd. Aspects of Mozart's compositions may lay the foundation for the opinions and musical ways of expression of other people studying the compositions, but the are not fundamental for the compositions themselves. By contrast, "feature" is something inherent to the object, and may therefore be fundamental for it.
I don't know if I'm making myself clear and it doesn't really matter anyway.

German term (edited): Sprachvertonung (or: Wort-Ton-Verhältnis)

Is what is meant in this context. To my knowledge, Wort-Ton-Verhältnis is the preferable German term. Studying medieval (and earlier) up to modern vocal music (e. g. J. S. Bach’s Cantatas, or F. Schubert’s song cycles “Die Schöne Müllerin” and “Winterreise”), you will encounter an abundance of musical means used to emphasize the meaning of the sung words. It would probably take more than one Wikipedia article to provide a more detailed explanation together with examples. (Surprisingly to me, I haven’t been able to find a single relevant Wikipedia article on this issue.)
Alternatively, you could use “word-music combination/relation”.

Examples:

http://tiny.cc/szSjR

http://tiny.cc/AY4KR

There was a close ***relationship between the words and the music***. Composers wanted to enhance the meaning and emotion of the text, and did so by means of ‘word painting’ i.e. : trying to project poetic imagery through link between music and words. As vocal music was more important, most music was sung a cappella.
http://en.wikibooks.org/wiki/Western_Music_History/Renaissan...

‘Dryden’s and Brady’s words,’ she avers, by way of example, ‘while delightful, are not in themselves musical...Though they praise music as a creative principle, they also move away from the ***relation between words and music*** conceptually’
http://sscm-jscm.press.uiuc.edu/v6/no2/walkling.html

The book will comprise a study of the various ways in which the ***relation between words and music*** has been theorised and practised, with a view to demonstrating how theology, a discipline which of necessity involves words, can comes to terms with and benefit from phenomena that cannot be reduced to the order of words, such as music.
http://www.st-andrews.ac.uk/itia/publications.html

The relation between words and music has always been a central issue in opera. How would you describe the way this relation works in The Gambler?
http://tiny.cc/8Jjjw

"Opera as Expression: Notes on the Relation between Words and Music," The Hudson Review, Summer 1976