[rab] No, you only had about half of them. There are a full *eight* main chords at the start of each of the first eight bars (which you gave a "plang" to), the first seven each having a "chong" on the lowest bass F of the piano halfway through the bar...

And now a piece that you might be able to guess, just from the rhythm that runs through the entire piece as a background, which I'll give two bars in italics
TUM-tiddly-UM-tiddly-UM-tum
TUM-tiddly-UM-tiddly-UM-tum...
Deeeeeeee, da-da-doo-da-da-da dee, da-da-deeeeeeeeee - Da-da doo-da-da-da-deeee.....

[JLE] Now that (number 24) is Ravel's Bolero.

*grin*

updating:
1. Bob the dog - ISIHAC Theme 2. Chalky - Coronation Street 3. HB - Some Mothers Do 'Ave 'Em 4. Raak - Thunderbirds 5. Kim - The Archers' Theme 6. rab - Roobard and Custard 7. Bob the dog - Pomp and Curcumstance, Edward Elgar 8. Lib - Blind Date 9. ZK - Dangermouse 10. penelope - Blue Peter 11. Watty - Porridge 12. Kim - Tom & Jerry [Fred Quimby version] 13. Herr Bratsche - Monty Python 14. Raak - Star Trek 15. Bob the dog - Dr Who 16. rab - Have I Got News For You 17. Darren - Bergerac 18. Chalky - The Sweeney 19. Darren - Rentaghost 20. rab's plang-chonger - Rachmaninov's Piano Concerto number 2 in C minor. 21. Dazed - Blackadder. 22. Darren's dum-diddliddle-dum-dit-dit ? 23. JLE - Mahler's Symphony No.2 "Resurrection" 24. JLE - Ravel's Bolero

I reckon Watty and Darren should be choosing the next two tunes , although Darren's No 22. [80's TV] has yet to be guessed

Clues? New tunes?

OK, here's 25 and it's 90s TV.

RattattattattattattATT!!
dada duhhhh, dada duhhhhh, dada duhhhhh da-da.
dada duhhhh, dada duhhhh, dada deeee da-da.
dada duhhhh, dada duhhhh, dada duhhh da-da,
da-daaaaa, da-daaaa, da-daaaaa, da-da.
(repeat from second line)
dadada daaaa-daaa-daa-daaaa, daaa-daaa-daaa-daaa,
dum-da-daaaa-da daaaa-daaaa-daaa-da,
dum-da-daaa-daaa daaaa-daaaa-daaa-daaa DAAAAAAA
(repeat first bit again)

Does anyone want a clue to number 22?

[Darren] Yes please!

[Brendan] OK, think Richard Briers.

Ever Decreasing Circles. A puzzlingly unrepeated top-quality classic...

[Darren] Number 25 - Men Behaving Badly?

[rab] re. EDC - funny, we were saying that only last night .. Howard & Hilda - a sublime coupling.

[Chalky] In exactly those words? That's scary. *sweeps the room for bugging devices*

[rab] yup - during Mother's Day Dinner. My sister-in-law has neighbours [married couple] who always leave their house in matching outfits so naturally the conversation turned to ...
[Darren] I won't attempt a guess at either of yours 'cause I think rab and penelope may be right

Are we out of challenges? If so, here's another "classical" one (26):

takatakataa takatakataa takatakata takatakatakataa
takatakataa takatakataa takatakata takatakatakataa
(continues behind ...)
daaa daa di dip dip, daaa daa di dop dop, daaa daa di dipdip
dee dee dee dee dee dip dip, dee dee dee dee dee dip dip
dee daaa daa di dop dop ...

[rab] Correct. It's one of my all-time favourites. [penelope] Correct.

[HB] Is it the "advance of the Nazis" moment in Shostakovich's "Lenigrad" symphony, first movement?

Um, "Leningrad"...

[JLE] Right in one. Note to self - try someting more obscure next time.