Many phonemic units can be readily described as a configuration of segments of acoustic features. Certain stop allophones, for example, can be constructed out of the features silence, burst release and aspiration. It seems natural to specify this as a rewrite rule that can be interpreted by a parser: stop <- silence + burst + aspiration. Conventional parsers construct grammatical phrases out of words. The words and phrases are discrete and follow each other in a well-defined order. Such parsers are not appropriate for acoustic segments because these are variable in length, and overlap each other or have gaps separating them. This paper describes the capabilities of a parser that has been modified to handle this kind of input.