Cryptic crossword No 100

Congratulations on being puzzle #100 Cormac! Quite an honour.

[SPOILERETTE I suppose...] As Laguna says, congratulations. This was a bit Marmite for me, I'm afraid. Some clues were quite superb - 1ac, 20ac, 24ac, and 26ac was the neatest clue of its kind I can remember seeing. But the fairly obscure musical knowledge required to complete the puzzle - 19ac, 8dn, 18dn, 19dn, - was beyond me. I wound up feeling sufficiently fed up that I Revealed 6ac even though GK was a musician (that's the spoilerette) I did know.

Thanks Cormac. There are some good wordplay constructions here. I think 14d is the best clue due to the clear image conjured up by the surface. (SPOILERS BELOW)