Before co-founding Spotify, Daniel Ek was chief technology officer of Stardoll. Stardoll was a browser-based game and fashion community focused on customizable digital dolls and social interaction.
Ek’s role at Stardoll was part of a remarkably early technology career. He began building websites and open-source projects as a teenager, then held senior technology positions before becoming involved in the company that would lead to Spotify. His experience in online communities and internet products helped prepare him for building a large-scale digital media platform.
After Stardoll, Ek founded the online advertising company Advertigo. TradeDoubler acquired Advertigo in 2006, and Ek’s work and financial success gave him the freedom to pursue a new project. He later co-founded Spotify with Martin Lorentzon in Stockholm.
SoundCloud, Myspace, and Skype are plausible distractions because all became important names in online music, social networking, or communications. However, none is the company identified as Ek’s pre-Spotify CTO role. Stardoll is the specific and canonical answer.