This is the 892nd most frequent Catalan word.
vella
Old (feminine).
In this case, 'vella' is used to describe the song, modifying the feminine noun 'cançó' and signifying its age or sentimental value.
La cançó vella em porta molts records.
The old song brings me many memories.
'Vella' is qualifying the grandmother, again as an adjective, to indicate her age while maintaining a positive connotation within the sentence context.
L'àvia vella encara balla als casaments.
The old grandmother still dances at weddings.
Here, 'vella' describes the age or state of the house, functioning as an adjective in agreement with the feminine noun 'casa'.