This week gave us a highly enjoyable puzzle from Aedites, and not too difficult for Gregson, who remembers listening to the piece on a vinyl LP many times as a child!
The extra letters indicated by wordplay in 22 clues spell out BASSOON SERGEI PROKOFIEV. In Sergei Prokofiev's "Peter and the Wolf" (first performed in Moscow on 2nd May 1936), the part of the grandfather was taken by the bassoon. Chambers defines the bassoon as a LARGE WOODWIND INSTRUMENT, which can be found diagonally across the grid in the approximate shape of a bassoon. Gregson had a brief moment of doubt about the position of the final T, but luckily decided to go with the more natural of the two alternatives.
In the following explanations, the extra letters indicated by the wordplay in the thematic clues are shown in square brackets.
ACROSS
1 Cut back stage degree in America (4)
S[B]NIP (PIN (stage) + BS (degree in America) all rev)
5 Short fight in uniform provides little warmth (8)
FLAMELET (MELEE (fight) minus last letter inside FLAT (uniform))
11 Frame guillotined musical monarch (5)
AIRER (HAIR (musical) minus first letter + ER (monarch))
13 Pest tucking into grandchild's fancy (5)
OP[A]INE (PAIN (pest) inside OE (grandchild))
14 Swell masculine thong! (4)
RI[S]EM (RISE (swell) + M (masculine))
15 Lyre string traps energy (4)
NET[S]E (NETS (traps) + E (energy))
16 Compact offices with a touch of elegance (5)
DENSE (DENS (offices) + E (first letter of elegance))
17 Jerry-built slender support (3)
LEG[O] (double def)
19 Vital urge held by John in the same place (6)
LIBIDO[O] (IBID (in the same place) inside LOO (john))
20 Evangelical Union regularly modulates Gregorian cadence (6)
EUOUAE (EU (Evangelical Union) + OUAE (alternate letters of modulates))
22 One man reverses first line in treble (5)
E-LA-MI (I (one) + MALE (man) all rev)
23 Contort heart - new move (7)
WREATHE[N] (anag of HEART NEW)
24 Iron words for burrowing rodents (7)
MAR[S]MOTS (MARS (iron) + MOTS (words))
28 Startled loner to enter … (5)
ENROL (anag of LONER)
30 … sandstone vessel standing still without power (6)
ARKOSE (ARK (vessel) + POSE (standing still) minus P (power))
32 Depart with drug commission (6)
OFFICE (OFF (depart) + ICE (drug))
36 Vintage unbleached linen … (3)
[E]CRU (double def)
37 … confused with male frill (5)
RUCHE (anag of CRU (previous answer) + HE (male))
38 Fool to talk cheerfully without note (4)
TWIT[R] (TWITTER (talk cheerfully) minus TE (note))
39 Inert matrix detains a Celt (4)
GAEL (GEL (inert matrix) round A)
40 I bestow the last word (5)
IDEAL (I + DEAL (bestow))
41 Recline after rebound of record jump (5)
[G]OLLIE (LOG (record) rev + LIE (recline))
42 Antibiotic befuddles many ettins without money (8)
NYSTATIN[E] (anag of MANY ETTINS minus M (money))
43 Scots bury tiny tie-rods ignoring odd bits! (4)
[I]YIRD (alternate letters of tiny tie-rods)
DOWN
1 Mount confuses in circular shift (6)
SADDLE (ADDLES (confuses) with last letter shifted to front)
2 Put back pies in issue from immigrant parents (5)
NISEI[P] (PIES IN rev)
3 Eucalyptus tree hit by gun report (8)
IRONBARK (IRON (hit) + BARK (gun report))
4 Miners' prom played something juicy (9)
PERSIMMON[R] (anag of MINERS PROM)
5 Tortured man with inducted current (5)
FRIED (FRED (man) round I (current))
6 Be still! - Hair's on end? - Keep quiet! (6, two words)
LIE LO[O]W (LIE (be still) + WOOL (hair) rev)
7 Arrogance is a gloomy or depressing situation! (6)
MORGUE (double def)
8 Art-song continued without heart (4)
LIED (LIVED (continued) minus middle letter)
9 Fish recoil following county bodies (5)
[K]ENTIA (KENT (county) + AI (fish) rev)
10 American monkey for abstainer (6)
TEE-TEE (double def)
12 Muslim prince heads a Middle Eastern economic rising (5)
AMEER (first letters of a Middle Eastern economic rising)
18 Courageously houses two ducks in a grumbling manner (9)
MO[O]ANFULLY (MANFULLY (courageously) round OO (two ducks))
21 Distracted Ruth ridicules losing rotten herds' bladders (8)
UTRICULI (comp anag RUTH RIDICULES minus HERDS)
24 Injure metal bird (6)
MARTIN (MAR (injure) + TIN (metal))
25 Callous flaps eliminating left apertures in sponge (6)
OSCULA (anag of CALLOUS minus L (left))
26 Dorsal plates occur in water gadflies (5)
TERGA (hidden)
27 Glasgow drunk in Hindu garment makes tree with nuts (6)
S[F]OUARI (FOU (drunk in Scottish) inside SARI (Hindu garment))
29 Scottish lamplighter on date had a lecherous look (6)
LEER[I]ED (LEERIE (Scottish lamplighter) + D (date))
31 Noisy and wordy when distraught (5)
ROWDY (anag of WORDY)
33 Not bound by rules concerning refrigerant (5)
FRE[E]ON (FREE (not bound by rules) + ON (concerning))
34 Railway support caught by locking spring (5)
CHAIR (C (caught) + HAIR (locking spring))
35 Rich man is gone (4)
DI[V]ES (double def)