Wunderlich is one of my favourite tenors. The sheer beauty of his voice always disarms me. However I find that this is taken just a bit too fast, which he means he cannot create an atmosphere of rapt stillness as the best versions above do. Not one of his best performances.He's much better in the ardent ebullience of a song like Heimliche Aufforderung.
I enjoyed Auger's performance. She has a better tempo, but her pure, girlish timbre lovely though it is, is not my preference for this song. Eisabeth Schumann also has a girlish timbre, but the tone is warmer and I like her use of portamento. She also has a better legato in the difficult first phrase.
"Morgen" is one of my favorite songs. I've long favored soprano Arleen Auger's version on her debut CBS LP from the mid-1980s. During this later stage of her career, Auger enjoyed kind of 'Indian summer' vocally, with her gorgeous voice remaining remarkably fresh at an age when most singers' voices have started to go into decline. She is accompanied by the excellent pianist Irwin Gage, & the sound recording is first rate. However, on CD, it was an early digital era disc & these days could use a fresh remastering (& hopefully will get reissued soon). Here they are performing "Morgen" live in concert around the same time,
Dame Janet Baker's studio version is another great favorite of mine, with pianist Gerald Moore:
In addition, there's a BBC recording from Baker at the Aldeburgh Festival, as well as a beautiful live performance of the orchestral version from Baker on You Tube, which are well worth hearing: