A Robust Parser-Interpreter for Jazz Chord Sequences

Hierarchical structure similar to that associated with prosody and syntax in language can be identified in the rhythmic and harmonic progressions that underlie Western tonal music. Analysing such musical struc-ture resembles natural language parsing: it requires the derivation of an underlying interpretation from an un-structured sequence of highly ambiguous elements— in the case of music, the notes. The task here is not merely to decide whether the sequence is grammati-cal, but rather to decide which among a large number of analyses it has. An analysis of this sort is a part of the cognitive processing performed by listeners familiar with a musical idiom, whether musically trained or not. Our focus is on the analysis of the structure of ex-pectations and resolutions created by harmonic progres-sions. Building on previous work, we define a theory of tonal harmonic progression, which plays a role analo-gous to semantics in language. Our parser uses a formal grammar of jazz chord sequences, of a kind widely used for natural language processing (NLP), to map music, in the form of chord sequences used by performers, onto a representation of the structured relationships between chords. It uses statistical modelling techniques used for wide-coverage parsing in NLP to make practical pars-ing feasible in the face of considerable ambiguity in the grammar. Using machine learning over a small corpus of jazz chord sequences annotated with harmonic anal-yses, we show that grammar-based musical interpreta-tion using simple statistical parsing models is more ac-curate than a baseline HMM. The experiment demon-strates that statistical techniques adapted from NLP can be profitably applied to the analysis of harmonic struc-ture

Intérêt de l'élastométrie impulsionnelle dans l'évaluation non invasive du stade de fibrose hépatique chez l'enfant. [Value of transient elastography in noninvasive assessment in children's hepatic fibrosis].

International audienceAIM: Transient elastography (FibroScan) is a novel, noninvasive, rapid bedside method to assess liver fibrosis by measuring liver stiffness. This study aimed to determine the feasibility and reliability of liver stiffness measurement in children with liver diseases. PATIENTS AND METHODS: Liver stiffness measurements were carried out on 72 children, from 4 to 18 years of age, with potential hepatic fibrosis disease. The clinical, biological, ultrasonographic, and endoscopic parameters were noted to identify children with portal hypertension syndrome. The APRI (ASAT-to-platelet ratio index) test was calculated according to the standard formula. An APRI test score higher than 1.5 indicates significant hepatic fibrosis. METAVIR scoring from 14 liver biopsies was compared to the liver stiffness using the Kappa statistic. RESULTS: Twenty-eight patients had viral hepatitis, 20 cystic fibrosis, 16 chronic liver cholestasis, 5 autoimmune hepatitis, and 3 patients had liver fibrosis with uncertain etiology. FibroScan measurements were available in all children. There was good agreement between FibroScan and pathological studies (weighted kappa=0.814). Only 9 children had portal hypertension syndrome with an average measurement of liver stiffness significantly higher than children without portal hypertension (26.5kPa vs 6.4kPa; p<0.01). The APRI test for 6 out of 9 patients scored higher than 1.5. CONCLUSION: These results indicate that liver stiffness measurement is feasible in children and seems to be related to liver fibrosis. Larger prospective studies are needed to validate this FibroScan method