Something very wrong here or I've messed up big style.
a) Consensus say 5d is OPINE, but according to my grid 5d only has 4 letters.
5d. A duck at the top of a tree, say (4) ???H. If 9a is ALTO then second letter is O - quashing my theory of DASH as the answer, leaving me with ?O?H.
b) DASH also seems to be the answer for 23d.
28a. Capital letter in many awful intro's (4) L??E