  This paper resumes the results of a research conducted in a music production
situation Therefore, it is more a final lab report, a prospective methodology
then a scientific experience. The methodology we are presenting was developed
as an answer to a musical problem raised by the Italian composer Marta
Gentilucci. The problem was "how to extract a temporal structure from a vowel
tremolo, on a tenuto (steady state) pitch." The musical goal was to apply, in a
compositional context the vowel tremolo time structure on a tenuto pitch chord,
as a transposition control.In this context we decide to follow, to explore the
potential of low-level MPEG7 audio descriptors to build event detection
functions. One of the main problems using low-level audio descriptors in audio
analysis is the redundancy of information among them. We describe an "ad hoc"
interactive methodology, based on side effect use of dimensionality reduction
by PCA, to choose a feature from a set of low-level audio descriptors, to be
used to detect a vowel tremolo rhythm. This methodology is supposed to be
interactive and easy enough to be used in a live creative context.
