Lots of old hits of A.R.Rahman's track are included in the BGM (Background Music) and dance sequences in D3.
Take an example in yesterday episode we heard different versions of "O Yuva Yuva" song from Yuva in D3:
1. First the usual O Yuva Yuva track.
2. High beat O Yuva Yuva track for Shivam's entry.
3. And then another version when Rey, Swayam and Sharon look at each other after seeing Shivam.
4. A different tune when Shivam gets down from the stair case to meet them.
5. Then they mixed the same song with "Give it to me" song by Timbaland feat. Nelly Furtado & Justin Timberlake.
6. Later they mixed it with the BGM from Mani Ratnam's Guru (the scene where Mithun gets hurt when goons attack him in the movie Guru).
I guess the BGM composer of D3 likes to play with "O Yuva Yuva" song from Yuva and tries to give new dimension to the tune depending upon the situation. It is not the first time but we hear the same song tune in almost all episodes.
The other Rahman hits included in D3 are:
1. "Khoon Chala" track from "Rang De Basanti" (courtesy: when Vicky, Neil gets hurt in yesterday's episode).
2. "Muqabla" track from "Hum Se Hai Muqabla" as BGM in many episodes.
3. "Hai Rama" track from "Rangeela" (courtesy: Swaron dance)
4. "Kya Karein Kya Na Karein" track from "Rangeela" (courtesy: Reyam's dance).
5. "Urvasi" song from "Hum Se Hai Muqabla" (courtesy: dance by D3 boys).
6. "Radha Kaise Na Jale" from "Lagaan" (courtesy: Kriyansh dance).
I might have missed a few as I made this list as per my remembrance. It is interesting to see many old Rahman tracks inluded as BGM and dance sequences in D3. I think A.R.Rahman's music company or the music label had given rights to include them as BGM / dance sequences in D3.