I understood it a lot better about 20 years ago when I was still playing every week! Now it's a bit like trying to remember quadratic equations - and for those people who tell you maths and music go hand in hand, they are lying - I played at a junior national level for years whilst barely being able to count past 20 and as soon as they introduced letters into maths I stopped understanding a thing!!
Music and dance are intertwined for me, often in a way I can't describe. Dave Arch, who does the arrangements for the band on SCD often does an amazing job, and sometimes with music that you think will never work in a million years, but sometimes even though the arrangement is technically sound, it doesn't hit the mark on the feel of the dance, which is why you watch it and think 'meh' and other times you watch something that shouldn't work and it stays with you for years but even then you need the staging and wardrobe to hit the mark too - think Mark and Karen's AT or Cha-Cha, Alesha's Cha-Cha to Crazy in Love, and Rachel and Vincent's AT to When Doves Cry.
As much as you need to music to create the atmosphere, if the rest of the concept isn't right, the music has an uphill battle that it can't always overcome. Years back, Mel B did a paso to 'Free Your Mind' on the US version of Strictly, which was a bit out there, but the costumes, choreography and lighting all came together (not to mention, she danced out of her skin that week) and it is one of my most memorable dances, even getting on for 10 years later.