Losing Track by Nudd

This puzzle commemorates a classic record album. Twelve clues originally incorporated the titles of the album’s twelve tracks but (true to form for vinyl) all of the tracks have been scratched - solvers will therefore need to reinstate the missing titles before solving the Losing Track clues.
In all remaining clues, the wordplay indicates the answer with an extra letter not entered in the grid. These letters in normal clue order give two cryptic indicators which should help to identify both the performers and the album. Solvers should appropriately complete the two unclued entries, and must finally highlight four thematic names appearing in the completed grid.
Chambers Dictionary (2003) is the primary reference.

37D   “Join by marriage” appears in (Track 1) letters (4)
40A   Kensington Gardens (Track 2) for secret society ? (4)
35D   Foot of  (Track 3) worn to irregular shape (5)
2D     Tease American showing up with (Track 4) in tow (7)
22D   (Track 5) - be first with two men in pursuit? (8)
12A   Hey - (Track 6) in Job Centre to show contempt? (3)
45A   Apply (Track 7) before entry (4)
18D   Priest periodically seen in cell in (Track 8) (4)
33A   Sloth - (Track 9) - following United around North America (4)
1D     Ruffian band member (Track 10) runs for North (8)
4A     (Track 11) for a little (7)
8D     Lacking enthusiasm, without transport, carped “(Track 12)” (5)
2    unclued - See preamble  (5)   
9    Settlement on doctor’s back garden?   (4)
13  County court judge of old has no answer to eccentricity   (5)
14  Game in open upland environment  (5)
15  Eliminate weak spots (4)   
16  Mexican dough corrupted master. (4)     
17  Cut ladies’ hair badly - it’s the end of the line  (8)     
19  Evil Caligula sacks University of France   (6)
20  Worried about Dryden adaptation (5)     
21  Italian leader fortified mound next to church (4)   
22  Find fault with a preamble before going out  (5)
23  US agent, cowardly (not base) in retreat   (4)     
25  Cheery cat story upset bird   (13)
29  Drunk - fined a bunch of fives   (4)
30  Instruments regularly  found in telephone outlets (5)
34  Roman ghost depicted in Schiele’s mural  (5)
36  Feeble light close to God - death personified   (6)
38  Angry bee quits irrepairable ruin for riverside dwelling (8) 
39  Superb band returns, penning first of singles   (4)
41  A blackbird or a collie dog ? - merely confused   (5)
43 Yogic position assumed by a sane ascetic?   (5)
44  Journey regularly over Poland’s first railway   (3)
46  Announces arrival of less hard ground  (7) 
47  unclued - See preamble  (5)
3  Loudly exclaim “England’s greatest all round sportsman? - Eff off “  (3) 
4  Roman Catholic Church retires Bishop Flint (6)
5  Showers of rainfall dropping in south disrupted biosynthesis (8)
6  Travelling basket, all-but Indo-European in essence   (7)
7  Wear down by means of poetry   (5)
10  Stupefying drink confused wee lad (5)
11  Old peer first in English exam  (4)
12  Become bedraggled having left cardi off (5)
24  Stop outlaw in Perth after vintage month   (8)
26  Home counties area head returns without acceptable group of students   (7)
27  Big noise (second in command) leaves High Karroo (4)
28  Alien rings half of car showrooms for audio range   (8) 
31  Windows starts to run Internet Explorer locally in secondary operating system.   (6)
32  Wary of foliage on track   (5)
33  Out of breath domestic help dragging pannier drove upstream (5)
34  Fix biathlon downing medicine in China pot (5)
42  People of fashion take gold colouring from hairdresser   (3)
To enter this competition, send your entry as an image or in list format,indicating the highlighted words, to quiz.man@ntlworld.com before the 8th February 2012. The first correct entry drawn from the hat will receive a copy of the new Chambers Biographical Dictionary  which has been donated by Chambers.