I have long been aware of the tenor Richard Tauber, and his reputation as a Mozartian; but it was only this weekend that I really appreciated what justly led to him being one of the great lyrical singers of the twentieth century.
With my brother, and at his instigation, I watched through a film version of "Lilac Time"; which is an operetta loosely about the life of Schubert, that uses Schubert melodies for its arias and choruses. This 1934 movie was called Blossom Time, and had been adapted as a vehicle for Richard Tauber; despite that he could not act at all.
The movie itself is hopelessly dull; with a silly script, woodenly performed (Tauber himself being the most ligneous of all); but about halfway through, "Schubert" does a public concert of some of his songs (in the plot, he is standing-in for a more famous singer - which is why the audience is initially so hostile).
Here is the full movie on video: The relevant section runs from about 46-56 minutes.
These small scale works demonstrate better than the operas I have previously heard, what made Tauber so special - and so famous for his technique and musicianship. Look out for the smooth legato style; by which Tauber sings continuously, with a flow of tone continuing uninterrupted between the notes.
The musicality of phrasing, and the way he subtly points the meaning of lyrics, are both features of the German Art Song (Lieder) tradition - and show Tauber's high level of musical intelligence and training.
He also displays the extremely difficult art of messa di voce; by which he can sustain a note while increasing or diminishing the volume, while maintaining the intonation and vibrato.
A further exceptional aspect is when Tauber sings extremely quietly (pianissimo) - again while maintaining tone, pitch, and with clear diction.