ACROSS

 1 How a character of The Oxbow Incident was upset making a projection. (11)

 9 and 10 Old song as a companion piece to “Dry Bones”? (1,4,3,6)

11 and 12 What the leper properly has. (7,7)

14 They lower the life-boats from them. (6)

15 Rose with 21 down. (8)

17 Leather has bad color, it seems. (8)

20 Sort of basic, when about one of a school’s three Indians. (6)

22 Comes out fighting on account of the wisecracks? (7)

24 Part of the liturgy is slowly changing, obviously. (7)

26 One might be found in a ring when 23, but one hears it is to continue stationary. (6)

27 1 across shouldn’t get over describing such things. (8)

28 Perhaps prudish, but at least it sounds as though the tie isn’t crooked. (6-5)

DOWN

 2 Descriptive of Grey’s 15. (9)

 3 Outbursts that leave the spirit in tatters. (7)

 4 How kitty might be made sweet and neat, possibly. (4)

 5 Originally a nonbeliever should be moderate about one. (7)

 6 This old coin should be easily distinguished. (5)

 7 Teddy found it right under him, in Arsenic and Old Lace. (6)

 8 Confuses, as does port. (6)

13 Shrewd, and able to briefly state the combination. (5)

16 How to shed some light on what they might do to the milk supply? (9)

18 See 23

19 She egged her brother on to vengeance. (7)

20 Not a drum was heard at Sir John Moore’s burial here. (7)

21 Supposedly not deep in the skin, especially with 25. (6)

23 and 18 Is it dangerous for a moth to be so like a dizzy blonde? (5-6)

25 Appearing with 23 on the stage notice. (4)