This originally appeared in the July 1997 Enigma, and was my first variety cryptic; many thanks to Hot and Trazom for their editing. The abbreviations MW, 10C, and NI3, as usual in the National Puzzlers' League, refer to Merriam-Webster, and their 10th Collegiate and 3rd New International Dictionary.

One-third of the 45 clue answers must be altered before being entered in the grid. The required alterations, all indicated by the title, are divided equally among three different types. Answers include five capitalized words. Five answers are not MW, although one is 10C-inferable and another, a foreign word, can be found in NI3.

ACROSS

1. Enigmatic emblem is tin-plated Greek letter chi (6)
8. Toothpaste is family property? (5)
11. One's as twisted as spring, perhaps (6)
12. Mustard, for example, is ground, not minced (9)
15. Vehicle path stretched endlessly westward (4)
16. Guy with cross bird (4)
17. Hrothgar finally invades tip of Scandinavia (5)
19. Bad eggs have, time after time, nettled principal (6)
20. Mathematical surfaces are craggy hillish things? (7)
21. Chevalier's among decapitated British moderates (5)
24. Sun god faces certain obliteration (6)
28. Holiday has to last for a month (5)
30. One can imprison bird for opposing IRS activities (7)
31. Those who select loud hues (6)
33. One eats revolting bird seed (5)
35. Queen misued Nair (4)
36. When invoked, Muses will give no reply to Schiller (4)
38. Sound, like /ə/ or /ō/, having no retroflex aspect (9)
39. Cowgirl had incomplete idea of stuff I and others are involved in? (6)
40. Sound, taut, canvas structures (5)
41. Insulted editor from Hell? (6)

DOWN

1. Many see dirt fused to become like sandstone (11)
2. Support for pawn (4)
3. Knave perhaps displays integrity (5)
4. In cadaver's head is gold tooth (7)
5. Relative that is in eastern half of France (5)
6. Topless singer in tavern has guts (7)
7. Cuban leader beheaded baseball player (5)
8. He who would enter Heaven must have encountered light verse? (7)
9. Portion of food with rodent upset no one (6)
10. 1000 drowned in a French river (5)
13. Alliance between two radicals is mired in confusion (5)
14. Direct mail held up by Ireland and Turkey's leadership (11)
18. Slowly work through "Two and a half times zero"? (4)
22. Loud noise from liner's aft propeller (4)
23. Wood ultimately wore thin (5)
25. Is present for test, and fails (7)
26. Obscure tunes I'd never located (7)
27. Upstanding judge collects '91's taxes (7)
29. Draw out a legal hearing (6)
31. Birdbrained castrato is performing after explosive opening act? (5)
32. Make fresh sausage without one upset (5)
33. Seize future queen? (5)
34. Pieces written after hero's termination! (5)
37. Egyptian god consumed Nubian leader (4)