Page  364 ï~~POC( AN ENVIRON] ANALYSING, MODIFYING EXPRESSION Henkjan H Music Department City University Northampton Square GB-London EC1 V OHB Centr Poco is a workbench for analysing, mod conte sic. It is aimed to use in a research tion musical objects and structure wa models of the same j surgery" c expression made it possible to c erformance and score data. New expression. A lot of attention and extendibility of the system. TNTRODlUCTTON

Page  365 ï~~When scores are available, computer assistance is indispensa mance and the score (e.g. taking care of performance errors, orc in the performance etc.), since we have to compare them on a sist in transfering structural information from the score to the j parts), instead of having to annotate each new performance. Of course the possibility of recording and playing back perfc ments is an important requirement, next to having access to lil scores, and employing graphical and textual editors in editing th All the means described should be embedded in a programmir mum flexibility and extendibility. The environment should sups of different versions of data and how it was created), assistanc( the same analysis over all the data of an experiment), and the au about the system. These are just a few demands on system supp Finally, both first-time and advanced users should feel comfo time users should be able to make use of menu's and dialogs, the actions that are performed. More advanced users probablyv using a programmed way of manipulation. The user interface and flexible, and it should be easy for advanced users to extend grams well integrated. We will try to give shape to this hotchpotch of dreams and

Page  366 ï~~I/O Communication with the outside world is implemented a, streams, a combination of a medium (e.g, a file, a windov (e.g formats, protocols) The system provides different i/( files) All information generated by the system is encodec there is always completeness of information. A new med by providing a set of read and write functions. We support the Midi standard to be able to use comme facilitating the exchange of performances and scores bets ng range of Midi based instruments and interfaces. The ft of information. Within the system the musical informatic resentation. DATA REPRESENTATION A consistent and flexible representation of musical obje cause all operations take place on this representation. Musical Objects There are two kinds of basic objects in this representatio tervals are note, rest, and segment (denoting structure) Ti fnrna tw nn \ nnmnt (frr rnrecnn t;n rnmmnnt acn A nth

Page  367 ï~~Another set of tools embodies some well-known models of c parser (1987), Todds model of rubato (1989), the Sandbrg (19 (Van Oosten 1990), and the Desain and Honing connectionist q formations that are available. typical path To give an idea of both the complexity of an expressive trans at first sight, and the support given by the systemin the realis describe a typical path from an original piano performance to a sive timing profile depending on the musical structure. To be able to look at the expressive timing of the performa score available in one or the other standard formats or we can formance using one of the quantizers (Desain & Honing 1989; first version of the score. Then we probably need to do some (more) structural information, correct errors etc. This can be system, after converting the score to a convenient format. But the score should be matched to the performance under exami mance, altering order of notes within chords etc.) All non-notc information annotated in the score is merged into the perforr matched performance and score, both with all the available s basic input to our transformations. We can now, for instanc a -

Page  368 ï~~the Centre for Knowledge Technology for their helpaa r Ton Hokken and Thera Jonker for thetr special support File Edit EuaI rools Windows POLO m 1 wv,, ca..wr 9 i.i. v. c