This is the 13645th most frequent Spanish word.
retornaba
"Retornaba" means "was returning."
In this case, "retornaba" is applied metaphorically to describe the action of a memory resurfacing repeatedly in the past.
La música retornaba a mi mente cada vez que recordaba aquella noche especial.
The music returned to my mind every time I recalled that special night.
The verb "retornaba" is utilized here to indicate the progressive return of calmness after an event.
Cuando la tormenta pasó, la tranquilidad retornaba lentamente al paisaje.
When the storm passed, tranquility slowly returned to the landscape.
Here, "retornaba" is used as the imperfect tense of the verb "retornar" to denote a repeated action in the past.