Marvel announced at SXSW 2014 in the US that it has updated its Marvel Unlimited subscription app to include audio into digital comics. The “adaptive audio” feature will first make its debut on issues 8 to 9 and 11 to 14 of Ed Brubaker’s “Captain America: The Winter Soldier.” Emmy-nominated composer David Ari Leon scored the storyline for these story arcs.
Adaptive means the sound effects adjust to your reading pace, meaning the music will loop if you linger on a page or you will be hearing the next music sequence if you tap forward. The audio can also be disabled if you want. Adding audio to back issues will happen on a case by case basis, depending on how the readers react to the new feature.
Source: The Verge