Researching second screen interactions that form a social soundtrack concerning a major broadcast media event, we perform statistical analysis on more than 800 K postings and 50 K blogs of Super Bowl XLIX on Instagram and Tumblr respectively for three categories (commercials, music and game) during three phrases (Pre, During, and Post) identifying the influence of different social soundtrack features of the postings on formality of contents during three phrases (Pre, During, and Post). For Instagram, the positive influence of URL-based postings in relative scale on formality is significant, but other features have significant negative impact in Pre and Post phases. For Tumblr, undirected broadcast pattern of conversation and number of sentences in relative scale in Pre and Post phases have a positive influence on formality. The During phase does not show any significant influence between any of the social soundtrack feature and formality of the postings for either Instagram or Tumblr. It is important to note that formality is significantly increased on Instagram, but it exhibits significant reduction on Tumblr. We further evaluate the effects of categories on top of the influence of social interaction features on contents of social media platforms for a fixed effects model. For Instagram’s formality aspect, the fixed effects estimate of the game category significantly outperforms the other two categories in all three phases, while for Tumblr, the music category fixed effects plays the lead role in Pre and Post phases. These results assist in identifying the strength of linkage among broadcast categories, social media postings, and inherent formality, providing insights into viewer reactions to the broadcast of In-Real Life events.