Twitter's investment in live video appears to have re-energized the social media site, but with stagnant user growth, its stock plunged early on Thursday.A large portion of Twitter's live investment is with music programming, and broadcasting concert events to bring remote users up close. It's pushed the newer feature with TV ad spot, "Music is Happening," which stars Chance the Rapper and David Crosby, and debuted just a month ago in June.Though it may not be attracting new users just yet, "Music is Happening" has been a hit with viewers. According to iSpot.tv, the ad has scored a 95.6% average view rate (percentage of impressions across all views of an ad) on 1,733 airings. It's also experienced a completion rate of 93.2% -- a high number of viewers watching the spot at least three quarters of the way through.(iSpot tracks TV ads 24/7 across linear, VOD, OTT and time-shifted viewings, from a panel of 10 million connected TVs)Based on where the ad's been placed, Twitter also seems to know where it's most captive audience may be. "Music is Happening" has received the most impressions during Late Night with Seth Meyers and the Tonight Show Starring Jimmy Fallon,  with over 30 million amassed during those two programs alone. Chance the Rapper has been a guest on Fallon's program before, and has been on fellow NBC show Saturday Night Live a few times in the last year or two as well.Some of the best attention scores for the spot came from sports programming, including ESPN shows NBA: The Jump, SportsNation and First Take all earning AVR scores above 98.7%.The service is still in its infancy, and admittedly, so is the ad (relatively speaking). So as long as "Music is Happening" appears to be resonating with viewers, the chance for live video to help Twitter grow its user base is still out there.