The alternative to Io having a techne is that he is possessed by a divine power. Socrates first uses the magnet analogy.

Io seems almost to challenge Socrates to tell him why he is exceptional as someone with a techne, in that he can talk well only about one practitioner of his techne, although Socrates' last example implies that Io does not have Homer's techne. The techne of poetry and the techne of rhapsody...