This isn't really the story I imagined I would be entering the AC fandom with, but here it is. I guess this is the light side to the Bleeding Effect.
Desmond created his playlist on accident. In the few hours he had outside of the animus, he retreated to everything that reminded him of himself. He used his phone for his familiar gaming apps and the internet and the music he'd gathered over the years he'd been on his own. He searched through youtube for something new and current and present and instead found a man that had taken an electric guitar to a traditional Italian tune. He watched the entire video, motionless and breathless. He watched it twenty more times before downloading it. It made him ache of home in a way much deeper than the music he had learned to listen to in order to separate himself from his life before running away.
Finding modern renditions of Syrian music proved to be a little more difficult. When he did find it, there had been synth beats and quickened paces rather than added electric instruments. Most of the titles had the words 'dance remix' in them, but the songs reminded Desmond more of flying across roof tops than dancing.
Desmond completed his playlist only weeks after finding the first song. He'd experienced Connor's first proper mission and came out of the animus only wanting to tell the boy what would happen just so he could come up with a better plan to help his people. He wandered around the temple for some time before slipping away to see the world again. He stayed outside, freezing, and staring at the stars dulled by city lights. He pulled out his phone and searched for music.
He found electronic remixes of the music from powwows and hoop dances and more. Most of it didn't actually come from the descendants of Connor's people, but Desmond found it to be enough. He had the proof he needed that his people lived despite knowing what would come to them.
He fell asleep every night after that with his headphones in and his playlist on repeat. The Abstergo employee who uploaded everything from the phone into their system never even flagged it as important.