Adjectives describing a mixture of masculine and feminine nouns

Question

I should know the answer to this question, but I'd feel better if I heard it from the community here. If I am using one adjective to describe more than one noun; one noun being masculine and the other feminine, which ending with the adjective take? For example, if I say:

Ha infundido los sonidos de la cumbia tradicional con los Blues, el Vallenato con instrumentos y armonías modernas...

"Moderno/a" is describing both 'instrumentos' and 'armonías', so should 'moderno' be 'modernOS'? I believe this will be the case, but I wanted to double check.

¡Gracias!

Steven

Answer 1

I believe that you're right. I can't find where I read that or what lesson it was, but I remember that rule.