mu+ is a system for corpus based speech research that can be used to retrieve and analyse segments and their associated signal files from a large speech corpus. The segments can occur at many different levels (acoustic-phonetic, phonemic, intonational, prosodic), while the signal files can include the acoustic speech waveform, analysis parameters derived from the speech waveform (e.g. formant frequencies), and various articulatory measurements (e.g. kinematic parameters from lip and jaw movement). Most combinations of segment types, together with their boundary times and the speech signal files with which they are associated, can be retrieved hierarchically (all phonemes that occur in certain words), sequentially (all phonemes that occur in a particular triphone) or hierarchically and sequentially (e.g. all phonemes that occur in content words which are preceded by an intonational phrase of a particular type). The segments and their associated signal files that are retrieved from the speech database can be analysed subsequently using a wide range of statistical primitives and digital-signal-processing routines. The system has been developed to provide a common environment for experimentation in numerous facets of corpus based speech and language research including: articulatory and acoustic phonetics, prosodic analysis, speech technology research, and linguistic corpus development.