Apex 2018 solution

The code phrase was KEYBOARD MUSIC, a genre particularly associated with CHOPIN, BRAHMS, COUPERIN and SCHUBERT.  Variations on KEY were keys on a computer keyboard; variations on BOARD were words that could be associated with it in compounds.

ACROSS

1              SNBQCL (CHOPIN); c + hop in

5              WIGWAG; wig wag

10           AUSTRIA; A US tria(L)

12           SYRIA; s + airy (rev.)

13           GET-GO; e.g. (rev.) + T(o’)go

14           MARM; R in mam & lit.

15           ESCAPE (Variation on A)

17           SATIE; ‘s a tie

19           SERENE; ere for a in sane

20           THE FLAT; t,h + E flat

23           IAGO; I ago

24           IRAQ; I r aq.

27           LINCTUS; ct. in Linus (Peanuts)

29           CURARE; Cu rare

31           BLASH; L in bash

34           DELETE (Variation on A)

36           OOZY; (W)oozy

37           ETAGE; tag in (w)ee(k)

38           OLLAV; ol(d) lav

39           ELENCHI; en in elchi

40           MARVER; m a r(I)ver

41           EMSTAF (BRAHMS); HM in bras(s)

DOWN

1              SAYEST; ayes in St.

2              NUTS; stun(t) (rev.)

3              CREPE; rep in CE

4              LITERAL; liter al(l)

5              WAGES (Variation on B)

6              ISOMER; I some R

7              GYMQRICL (COUPERIN); coup Erin

8              AIRING; A1 Ring

9              GAME (Variation on B)

11           SECT; cf. tecs

16           NEAT; neat(h)

18           IFQAOYAV (SCHUBERT); sch. (p)ubert(y)

21           EARL; cf. Lear

22           TINDALE; anag. in tie

25           RUCOLA; ru(e) cola

26           GRIEVE; g + I in ever (rev.)

28           SHERIF; H in fires (rev.)

30           ENTER (Variation on A)

31           BEGEM; e.g. in BEM

32           AESC; cf. aces

33           ROOM (Variation on B)

35           TAHA; hat (rev.) + a

As always there was a clue-writing competition, with KEYBOARD MUSIC being the phrase to clue.  Here are the top three:

1st  Moby Dick sure is complicated without a set of notes   (Ross Beresford)

2nd Scenes from Childhood, eg your backside getting spanked after admitting a bit of mischief                   (Richard Heald)

3rd  I’d back my Euros to convert into notes for a grand?   (Richard Morse)