Yes and no: Snufkin is mostly seen with a harmonica, yes, but the guitar from this version, contrary to popular belief, does take from the source material, too: he sometimes was illustrated playing a flute, a guitar and a accordion, hence why the Fuzzy Felt Stopmotion™ Snufkin from the 70's was depicted mostly with a flute instead of an harmonica. Canonically, in the source material, he played all of those instruments but mostly harmonica. Different adaptations depict different instruments as his main one depends on the tone they're trying to achieve/how they personally interpret Snufkin. The people behind the Fuzzy Felt™ saw him more childish, as if he were Peter Pan, while the people behind the 60's and 70's anime saw Snufkin more as a "cool silent senpai" sort of dude.
