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Grammar rule hum_interp_hook//1
 hum_interp_hook(-I:interp)// is det[multifile, data('pack/mirror/5b/af/5baf525db02cf5cc8e6c5569f5e247d95be1578d/prolog/humdrum')]
This should be a DCG predicate that parses characters from a Humdrum token that signify an interpretation and returns a term encoding the interpretaiton. See interps.pl