Word for a sudden phrase completing/changing a memory
Solution 1:
The word I would use is Proustian, particularly when the memories are brought to the surface through the sense of taste.
Solution 2:
Anamnesis describes the recollection or remembrance of things past; for example, this CD is titled "Anamnesis" as "a lure to memories that live in music."
(Proust's novel might have been less successful had he called it Anamnesis, however.)
Solution 3:
it might be evoke : To call to mind by naming, citing, or suggesting.
Songs that evoke old memories.