No. 23 is a study in ascending slurs, nearly all of which cover compound intervals. There are probably a number of approaches to working this one out, but I think a big key is efficiency. Suggested tempo is quarter note=88-92.  Here are a couple of thoughts for practicing. 1) Buzz the intervals on the mouthpiece 2) Transpose the lower notes up an octave 3) Practice the slurs by playing them as harmonic series glissandos.