Feasibility of the detection of choirs for ethnomusicologic music indexing

The music is commonly structured in terms of the three classical categories which are instrumental, singing or singing-instrumental parts. To refine this notion, the number of singers and/or instruments is searched. An important difficulty appears when a choir in unison is observed: several singers try to reach the same note at the same time and the classical pitch analysis fails. This paper presents a method to detect such situation in an a capella context (without instrument). The approach is based on a temporal segmentation followed by a frequency tracking inside located frequency bands; it exploits the apparent splitting of the high harmonics due to small difference between the singers. The first results obtained on ethnomusicological corpora are quite satisfying and offer interesting perspectives to our work.