The phrase "tunes in" refers to the act of listening attentively or adjusting a radio or television to a particular station. Some synonyms for this phrase might include "listens closely," "attunes," "tunes into," or "fixes on." Other related words might include "hears," "perceives," "monitors," or "detects." When describing a more active process of selecting or searching for a particular channel or program, synonyms might include "scans," "searches," "explores," or "tests reception." Ultimately, the appropriate way to describe the act of "tuning in" may depend on the specific context in which it is being used.