We tested whether the emergence of familiarity to a melody may trigger or co-occur with the processing of the concept(s) conveyed by emotions to, or semantic association with, the melody. With this objective, we recorded ERPs while participants were presented with highly familiar and less familiar melodies in a gating paradigm. The ERPs time locked to a tone of the melody called the "familiarity emergence point" showed a larger fronto-central negativity for highly familiar compared with less familiar melodies between 200 and 500 msec, with a peak latency around 400 msec. This latency and the sensitivity to the degree of familiarity/conceptual information suggest that this component was an N400, a marker of conceptual processing. Our data suggest that the feeling of familiarity evoked by a musical excerpt could be accompanied by other processing mechanisms at the conceptual level. Coupling the gating paradigm with ERP analyses might become a new avenue for investigating the neurocognitive basis of implicit musical knowledge.