This is a method and installation in which a time-domain digital audio signal is split into a plurality of narrow-band time-domain digital audio signals confined to specific frequency bands, short-term segments of which are temporarily stored in memory. The method comprises the use of signal processing algorithms for extracting multiple signal features from said short-term segments in a fixed sequence or upon request from a decision-making algorithm. Said decision-making algorithm makes tentative or final decisions about the type of occupancy of frequency bands resulting from the extracted features. Said decision-making algorithm may request from said signal processing algorithms further specific feature extractions from specific short-term segments and make further tentative or final decisions about the type of occupancy of frequency bands resulting from the requested features. Next, said decision-making algorithm stores its tentative decisions and makes final decisions about band occupancy for processing together with results from later short-term segments. Eventually, said decision-making algorithm outputs final decisions derived from current and past short-segments in the form of a set of notes having been played over some recent time interval, together with information as to the timing of each note from the set.