Here is a 1-paragraph summary of the text: Music Hack Day San Francisco is approaching, and this year it will coincide with the San Francisco Music Tech Summit, making it an exciting event for music enthusiasts and developers alike. The previous Music Hack Day event in New York City was a success, resulting in 72 hacks presented, including Callaboraoke, a karaoke app created by VEVO team members Marvin Li, Antonio Melis, Leon Yu, and Plushcap using Twilio's API to enable real-time singing with friends over phone calls. The app went through rapid prototyping on .NET, showcasing the power of collaboration and innovation during the event, and even received recognition from MusixMatch for one of their prizes.