The bard's Bardic Inspiration feature states:
You can inspire others through stirring words or music. To do so, you use a bonus action on your turn to choose one creature other than yourself within 60 feet of you who can hear you. That creature gains one Bardic Inspiration die, a d6.
Once within the next 10 minutes, the creature can roll the die and add the number rolled to one ability check, attack roll, or saving throw it makes.
This basically plays out to be "You can do it!" or "Break a leg!", or just playing their lute to build suspense, to affect one thing at a time.
However, I was thinking about the possibility of changing this up for a more "constant" variation. A smaller pay off (+2, for example) for the entire period, much like listening to your favorite song when doing something challenging; Eye of the Tiger or Danger Zone during a fight, Stayin' Alive while doing a heal or revive check, or just your favorite song to get you in the zone, and your blood pumping.
Additionally, the original time frame is "in the next 10 minutes", which means any time within the next 60 rounds; so a compromise of a constant +2 over say, 1-3 minutes (i.e. the length of your "inpirational boom-box music") would not only fit combat more effectively, but also be more evenly balanced in bonus:duration ratio.
So; would a constant bonus of +2 over a shorter duration (1 minute) be balanced?