To be fair to you, Williamseal, I had never heard of this song before this week either. You can find it easily by Googling the second letters message. This excludes 16Ac, 21Ac, 33Ac, 9Dn, 18Dn, 23Dn. It is (3, 6, 3, 4, 2, 4, 3, 4) The important number you require from the preceding line rhymes with the last 4 letter word. This number gives you the nth letters from excluded words in 16Ac, 21Ac, 33Ac, 9Dn, 18Dn, 23Dn, which must be placed in front of the protagonists from the preceding line. You then have to identify 20 of the newly formed protagonists (5 diagonal lines of 4 symmetrically placed). The non participants (6) are 5 obviously excluded from the 20 by their nature and one usually included but infiltrating the diagonal line of the obvious non participants. Beware of 7 down's 7th letter.