hi john, how did i know you would ask this question?
the languages of west africa tend to be tonal and therefore drums are conducive to reproducing verbal messages. however, there is also an emotional message embedded in the music which words can only attempt to crudely and clumsily explain.
the maninka/bamana/susu drum language has almost totally been lost. abdoulaye diakite has talked about the solo he learned for ngri from his teacher. that solo is supposed to tell the story of a famous dancer's pregnancy. he has also talked about one of the 'passport' djembe phrases, citing a bambara phrase that corresponds to it. however, it's pretty hard to find a maninka/bamana teacher that knows such things. in nigeria, ghana, togo and benin you will readily find drummers who know the drum language which directly corresponds to tonal speech patterns.
in senegal, where wolof is the dominant language in much of the country, many drummers will take a sabar accompaniment phrase or bakk and be able to tell you what it means. for instance, taggu mbar contains a prayer reproduced on the drums. we have a sabar master here called pape mbaye who showed me how sabar soloists can convey hidden messages in the music. a regular wolof person will miss it, but a drummer who has gotten used to the sabar drum language (not difficult for a wolof speaker) will be able to understand. he demonstrated a phrase and then said to me what it meant in wolof. he said one time he heard a soloist use that to another drummer who was picking up the money that someone had thrown to the first drummer for his solo performance. the phrase he played for the benefit of the other drummer translated to: 'hey motherfucker, leave my money alone!'