Elementary

 Preamble

All clues are normal, but are divided into four sets of twelve solutions each, as follows:-

A) A     Each solution is entered with one letter added – the added letters could be rearranged to form BAND USES DEMO

B) B     Each solution is entered with one letter subtracted – the subtracted letters could be rearranged to form GROUP FOUNDED

C) C     Each solution is entered as a single word anagram

D) D     Each solution is entered normally.

All resulting entries are real words or proper nouns. Taking one original solution from each of the three sets will provide a musical group, three current or former members of which appear as entries in the final grid which should be highlighted, together with one of their hit singles (nine letters in a straight line, enabling the central square to be completed).  Four clue solutions provide two other hit singles by way of confirmation.  All enumerations refer to the length of grid entries.  One solution is in Collins.

Maurice / Verdine WHITE (38a), Philip BAILEY (6d) and Ronnie LAWS (12a) are/were three current or former members of EARTH (35), WIND (38) & FIRE (26d).  Their hit singles included LET’S GROOVE (24/41) and BOOGIE WONDERLAND (9/1d) and SEPTEMBER (highlighted diagonal – which with the help of the letter string in the preamble also resolves the two occurrences where the added letter is otherwise unchecked at 24a and 3d).

Solvers' Comments

Either the description was very generous, or I've been listening to this song too much, because my very first action was to pencil in "September" down the diagonal. Anyway, this was a lovely puzzle with clues that made me grin.

The four methods of entry provided an interesting challenge. After a lot of cold-solving, the single-word anagrams became relatively easy to spot, and the provision of the letters added and subtracted kept the level of difficulty to a C-grade.

I suppose it was deliberate that WATER is the answer to a type D clue. I tried to see how much I could enter without guessing and without using that the final entries are real words, and was happy that most of the grid could be filled under these conditions, but obviously several of the added letters appear in unchecked cells so I eventually had to check if some things were real words.

I was able to cold-solve many of the easy clues, which helped with the grid entries. The title should have guided me to the key words for the group, but I Googled 'September' as soon as I saw it in the diagonal and got the group that way. I do remember the group's name (though not the members) but I don't think I ever listened to their music. An enjoyable puzzle with an accessible theme.

I think I looked from elementary to Group to Band in the intro and preamble and leapt to Earth Wind and Fire. But that is as far of my knowledge of the group went so still spent a while on that there wikipedia and yon youtube reading and listening (often simultaneously, though that does make also drinking a cup of hot cocoa trickier). Not completely convinced my cup of tea, music-wise, but the crossword was good. Thanks.

Very well put together, with much to keep track of during solving. With grid almost complete, SEPTEMBER looked promising and handy pub googlers confirmed the group and names. Why are so many pop themes based on modern rubbish instead of the proper artists and songs of the 50s/mid-60s? Many setters are old enough to remember them, and the youngsters could easily find them on the net.

I think this represents the real gain the internet has given us. What might have been a relatively obscure niche, dividing solvers into those of the precise age and everybody else, has become perfectly fair and researchable general knowledge.

Nice variation in answer treatments added to the entertainment. Particularly liked 32 across. Spent a while looking for the third member before deciding White was doing double duty - sneaky! (Or I’ve missed something.)

Interesting variety of turning answers into lights, which needed a careful bit of 'book-keeping'. SEPTEMBER was easily found and the rest followed quickly from the internet. Having finished the puzzle, I thought I better listen to September to hear the masterpiece that had attracted Eclogue's attention. That was a big mistake!

Well worked, and a nice reminder of some classics (it set me off on a greatest hits trail via Apple Music).

It isn't often that I get the theme of a puzzle before solving any clues, but it happened on this occasion. Considering the various threads that needed keeping track of, I was actually quite grateful to know what was going on so early on. A terrific tribute to a great band, and it was particularly good to see just so much thematic material included. Many thanks, Eclogue.

Gosh, Earth, Wind & Fire have had so many members, chances are a Magpie subscriber has probably been in the band at one point or another. Not me though... far too young. In fact, they were on the curriculum when I did GCSE music as a textbook example of disco. Fun puzzle, thanks for getting September stuck in my head for a day or two.

Nice puzzle, plenty of thematic matter, not too tricky. Thanks to Eclogue

Crossword about a band, and Wonderland is the first clue solved. Nothing to see here. Eventually the penny dropped: brought a smile to our 50 something faces. Sometimes I think we should set a timer for 5 minutes to discuss the title only before thinking about any clue - we'd have got Earth Wind & Fire after about three minutes if we'd thought about it.

Great title for a fun tribute puzzle! Unfortunately I only know the tune to like two bars of the chorus of "September," so I spent 75% of the puzzle singing something like "all we are, rhythm is a dancer; all we are, we are, we are" over and over in my head. I'm fairly certain that none of those words is correct. I didn't realize until a while after I'd finished the puzzle that I was solving it IN September. Looking up the other two hit singles helped me finish the puzzle, as I was having a difficult time with the grid-fill. So thank you for that: the "confirmation" was more like a strong hint to me! I like that each element corresponds to a different way of entering entries into the grid, including WATER entered normally!. To me wind, rather than earth, seems more like an "anagram" element; it's a shame there are no anagrams of WIND. If only they'd named the band Earth, Air, and Fire, we could have had RIA, FIR, and HEARTH or something. The entry gimmicks made filling the puzzle a lot harder than it would be otherwise, but I thought the added challenge was fun.

Very nice - liked the four different elements of the clues and there was some fiddly bits with the additions so hope I got it all right.

I enjoyed this: so much thematic detail crammed into the grid. My only slight criticism would be that the preamble and title gave a little too much away (even though it's not a band I know much about) ... so there wasn't really a hugely epiphanous PDM. But the four entry modes were inspired, and the finish was quite tricky (still not 100% sure I have all the added letters right). Kudos.