[Latias is forever pinged by anything musical. So when she's idling through the school, wondering if there's any other classes she might be interested in taking and hears it, the Pokemon diverts from her course to go investigate.
She floats in, low to the ground so she doesn't startle too much. That would be sad, to stop such pretty music. She sways a little in time with the tune, and can't stop herself singing along a little in her natural, bird-like voice. Pretty music!]