This paper concentrates on recent extensions and applications of the well established SDIF Sound Description Interchange Format: SDIF selection is a standard way to access a part of an SDIF file. It allows users to select SDIF frames of a certain type and time, and certain parts of the matrix data. It can be appended to a file name, making it easy to use for command-line programs. Other applications include choosing output description types, or mapping them to display modes or actions, e.g., when converting from untyped legacy formats. Foreign programming language interfaces allow processing of SDIF data by languages other than C. Interfaces and support functions for Lisp (CLOS) and Matlab are presented. Dispatching file I/O is a new programming style to be supported by Ircam's SDIF library. Users of the library specify a set of callback functions each with an SDIF selection indicating the frames and matrices that should be passed to that callback. The library takes care of reading the file, and dispatches selected SDIF data to the appropriate callback(s). Writing works analogously. The applications described in this paper include utility programs for Unix and Macintosh for conversion, viewing, extracting, and merging of SDIF, the integration of SDIF into the widely used software-systems Additive, jMax, Max/MSP, Diphone, OpenMusic, and the synergetic effects induced. We propose an SDIF Frame Directory, which allows rapid random access to data at a given time in an SDIF file by recording the file position, type, time, and other information about each data frame in an SDIF file.