Well, the first difference is that they have an orchestral accompaniment, rather than piano. However, as against this, many of both Mahler's and Richard Strauss's songs that are heard with orchestral accompaniment were original written for performance with piano only. The major difference is that the later composers' songs are written in a high romantic idiom. As a matter of interest, some of Schubert's songs were orchestrated by Max Reger, ina similar style. Is that right or wrong?
Do they detract from the poetry? This is a far more interesting question. As Strauss put it in his opera 'Cappricio', 'which comes first, the music or the words?' Since I don't know German and have never read Goethe, Heine, Eichendorff etc. in the original. a musical setting doesn't worry me. However, when it comes to settings of English poetry, it becomes different. How can I ever read Christina Rossetti's 'Silent Noon' without Vaughan Williams setting coming immediately to mind? Gerard Finzi write an (orchestral) setting of one of Wordsworth's greatest poems, 'Ode on Intimations of Immortality' Fortunately, the music is not that memorable. However, Vaughan Williams setting of part of Milton's 'Ode on the Morning of Christ's Nativity' in his Hodie takes the words to another level (in my opinion), However, I have a friend who says he would never wish to listen to such settings as it would ruin the poetry. Sorry, if I have strayed from the point somewhat!
