Cryptic crossword No 3,640

Across

1. Fiddle opened Old As The Hills in session (8)
2. Pair of punks in Slayer (8)
3. Two Americans with new church practice (6)
4. Eighth note trill (6)
5. Harmonious pop group replaces soprano with alto line (11)
6. Regularly seen germ protein (6)
7. Female dead in vehicle (7)
8. Put away without storage space? (6)
9. Musician wanting bread money—painful to listen to (8,3)
10. Force one's case (8)
11. Couple's commitment (3)
12. Man following contralto round (6)
13. Poetic form has English lines inspired by section of Mass (8)
14. Fresh piercing (3)
15. Mysterious void in heavens (6)
16. American uncle goes back to Kansas after international organisation shows true face (7)

Down

1. Strengthen flavours in ewe-cheese somewhat (5)
2. Tuning a triad by ear (6)
3. Flog dodgy beer to the audience (7)
4. Half muted, truly sweet-sounding (7)
5. Transposed like a song? (7)
6. Second quarter note in primarily Arabic Middle Eastern scales (7)
7. New entrant playing in one octave (9)
8. Counter journalist's viewpoint (4)
9. Characters from low-class Japanese society (4)
10. Dish on our menu for Vix (6,3)
11. What muffles guns used without hesitation by lawman (8)
12. Tops on French pans (8)
13. Sang air playing fiddle in Mumbai (7)
14. Ordeal before being brought down in hunt (5)
15. Word of law, according to Caesar, leads to Europe's mightiest empire (6)
16. Date head over heels, enthralled by fragrant bouquet (7)