Answer: Violin or piano
Step-by-step explanation:
I assume 'o plano' meant piano and you made a typo. But both of these instruments have a wide range of expression, both being used for classical, indie, rock, etc. I would exclude trumpet and xylophone because you can't change their dynamics very much. I would lean towards piano, as it's likely to be used in more romantic pieces, especially considering piano duets are popular.