Tako tried to eat the guy's fingers several times, so I don't think they really had a "relationship" as he seems to suggest. Still he managed to find the motivation that inspires an octopus so that's a big deal!

Clearly, it wasn't wishful thinking, Tako did play the notes to get the crab so he was responding like an intelligent creature, not a creature acting only on instinct.

It would be amazing if he played a song, but the fact that he played any notes at all is pretty damn cool too!