This is the 7672nd most frequent Catalan word.
cantaves
"Cantaves" means "you sang" or "you were singing" (second person singular, imperfect tense).
In this sentence, 'cantaves' is used as the imperfect past tense to describe an ongoing action in the past that was interrupted by another event.
Cantaves una cançó molt bonica quan vaig arribar.
You were singing a very beautiful song when I arrived.
Here, 'cantaves' is used to indicate a repetitive or habitual action in the past.
Cantaves sovint a l'escola quan eres petit.
You used to sing often at school when you were little.
In this example, 'cantaves' refers to a specific action in the past as a comparison to the present.