The music track MUSExploreDay06 [MUST:0010486B] is used in Vanilla only in one situation: while viewing the ancient past during Elder Knowledge to witness the Ancient Heroes use Dragonrend on Alduin to learn that Shout. However, MusExploreDay06 is given a standard set of conditions for daytime wilderness explore: between 8AM and 6PM. Dawnguard additionally adds a condition for it not to be during a blood eclipse as well.
If you peer through time via the Elder Scroll at the Time Wound outside of that time (or presumably if a Blood Eclipse was happneing), no music will play during the flashback.
I do not know if music tracks have implicit fail states if no conditions are set, so deleting the Blood Eclipse GetIsCurrentWeather condition check and setting the GetCurrentTime checks from >= 8 to >=0 and <=18 to <=24 should ensure it can run at any time it's called for that quest.