 The most significant feature of HADES was the incorporation of a procedural language known as "SPIEL" (Signal Processing Interactive Editing Language) that provided for the creation and customization of specialized analysis procedures that can be stored as text files, edited, etc., and are similar to functions and subroutines in programming languages like C and Fortran.HADES was one of the earliest signal processing systems with an integrated language and, through the use of SPIEL, provided for automated procedural analysis of large datasets, usually speech data or multiple-channel physiological data acquired with specialized hardware such as the EMMA magnetometer system.Previous systems at the time included "ILS" from STI, Inc., and the MITSYN system designed by Bill Henke.