Riddles By Gnomie -October Crossword Centre

[Matakari]

A toughie with the following preamble:
Four unclued solutions, three of them translated from the original and one which is the work's title, are given as the answers to riddles in a work. The first and last lines of an aria from the work appear in the grid. The wordplay of every clue produces an additional letter that is not needed for the solution. These, read in clue order, give a further instruction.

Would like to see how far I can reach with this one. Answers to the following should help me to progress, thanks!

ACROSS:
17 A reprehensible senior journalist humbled (6): ??A?E?
31 Philosophical belief including obscenity in fact according to Voltaire (7, 2 words):????AET
39 Window to the sky, mostly related to gospel writer (5): L?T?O
46 Leader of technicians going into 'how' in promotional leaflet for stage contraption (8):??????E?
48 Building material of constructed basements etc - to seal principally (14, 2 words):????????P??I??

DOWN
11 Little boats' special promenades essentially prescribed on aft and fore of ship (11, 2 words):S????D?A???
22 Closely united but not initially celebrated (5): ?O???
26 Following stage of journey, returning, sell up for jokes (8):I?G?????
30 Functioning in commotion at regular intervals (6): ?O????
37 Vigour and spirit in Ed's magical, medicinal plant (6 ): ?ER???
40 Rambling detour's the road to take (5): CO???

[JJ109]

48 Asbestos Cement (anagram of "basements etc to s(eal)" Extra letter T

[Neveracrossword]

The answers to 11 clues in a tough puzzle will certainly 'help you progress', Matakari!

You have wrong letters in some - 31. 39, 40...
I'm trying to come up with some hints.

[roslyn251254]

17a a base (e)d
31 your A is wrong ...french 2,5
39 Only your L is correct ...relates to the 4th gospel writer bible
46 the leaflet is a flyer + (h)ow + T anagrammed

[roslyn251254]

11d little boats is the defn split 5,6
22 celebrated is the defn
26 split 3,5 jokes is the defn
30 on = functioning N is extra inside 5 letter synonym of commotion
37 defn is medicinal plant
40 anagram of detour missing one letter ....road to take

[Neveracrossword]

Thanks, Roslyn, I hadn't got very far (real life had got in the way).

Matakari, hope the rest of the puzzles becomes a bit easier now. I enjoyed it very much.

[Matakari]

Many thanks, Roslyn !

[Matakari]

A pleasant Monday morning to all! Happy to have enjoyed a weekend with successfully completing Mephisto and the Sunday Times Cryptic crosswords! Now I'm back to take up again the challenge of the Riddles by Gnomie. Some hints from Roslyn got me a long way, but I'm still stuck on a few for which I seek more hints. I would really like to crack this one and learn something! Thanks in advance!
ACROSS:
15 Fashions for wry faces long ago (4) : ??E?
19 Beasts' enclosure unserviceable for family of birds (5) : ??R?S
25 Believer in taxonomic theories equipped international coterie (7) :
?LA?I?C

DOWN:
2 Shelter mostly and portable winch set up for Perth's vehicle protection (6, 2 words) : RO?B??
7 American heroin casually turning up in cooking ranges (4):
AG?S ( AGES) ?
37 Vigour and spirit in Ed's magical, medicinal plant (6):
?ER??N ( HEROIN)?
38 Produced dull surface on coarse metal (5) : ???PE
43 Arrange to pour water on Ian's fag end (4): ??PT

[Neveracrossword]

2 Perth is the Australian one...
43 Your P is wrong. The answer is a Scottish word for the stub, end of a cigarette.

[Matakari]

A bit lost with this one, Neveracrossword:

2 Perth is the Australian one...

[Neveracrossword]

Australian, Perth, word, rather than Scottish, Perth, word.

[grumpy01]

7dn Agas?

[ProfessorMaisie]

AGAS is right A +(reversed) S[c]AG = heroin ['c' extra].
15 take the extra 'd' out of a 5 letter word for 'fashions'
19 take extra 'i' out of a 4 letter word for a beast's den + US
25 (your 'c' is wrong) 4 letters for 'equipped'/dressed in + I + S[e]T - 'e' extra

[Matakari]

Ok, any help for the others? Not that easy to formulate hints!

[ProfessorMaisie]

37 not 'heroin' - 5 letters for 'vigour'/elan + [i]N - 'i' extra
38 your 'p' is wrong - the obvious word for 'dull' but 'made dull' means putting E[d] on the end of it (with the 'd' extra).

[ProfessorMaisie]

43 is Scots slang that you might not know, so - 'arrange' = DO + 3 letters 'pour water on' with the middle 'e' extra.

[ProfessorMaisie]

...and for 43 your 'p' is wrong.
There are lots of obscure words/definitions in this puzzle.

[ProfessorMaisie]

...for 2d 'shelter' = 4 letters for a house part + [c]RAB for the 'winch'

[Matakari]

Gradual and interesting headway with this one, thanks to your guidance!
Now to verify the following:

15(A) Fashions for wry faces long ago (4): MOES

46(A) Leader of technicians going into 'how' in promotional leaflet for stage contraption (8): ?LYT?U?R

47(A) In Holyrood, purposes of upset drink left finally by the French (6): ET?T?S
( ETITES Or ETITIS ) ?

27(D) Of castle constructed of mineral found in dolomitic limestone, say (7) :
T??C??? ( Thought of TACTITE, but this clashes with 39 (A) Window to the sky, mostly related to gospel writer (5) = LUCAN

37(D) Vigour and spirit in Ed's magical, medicinal plant (6) : ?ER??N ( VERVEN ) ?

And finally, a HINT for
42(D) Old white gannet turning up in inner temple (4) : ???S

[Neveracrossword]

Matakari, just a quick point... I thought a brief mention of Australian Perth/Scottish Perth would help. As you've been doing puzzles, including the Spectator, for over a decade, I was sure you must have encountered the use before now!