Section: Research Program
Participants : Arshia Cont, Philippe Cuvillier, Florent Jacquemard, Maxime Sirbu, Adrien Ycart.
When human listeners are confronted with musical sounds, they rapidly and automatically find their way in the music. Even musically untrained listeners have an exceptional ability to make rapid judgments about music from short examples, such as determining music style, performer, beating, and specific events such as instruments or pitches. Making computer systems capable of similar capabilities requires advances in both music cognition, and analysis and retrieval systems employing signal processing and machine learning.
Machine listening in our context refers to the capacity of our computers to understand “non-speech sound” by analyzing the content of music and audio signals and combining advanced signal processing and machine learning. The major focus of MuTant has been on Real-time Machine listening algorithms spanning Real-time Recognition Systems (such as event detection) and also Information Retrieval (such as structure discovery and qualitative parameter estimation). Our major achievement lies in our unique Real-time Score Following (aka Audio-to-Score Alignment) system that are featured in the Antescofo system (cf. Section 5.1). We also contributed to the field of On-line Music Structure Discovery in Audio Processing, and lately to the problem of off-line rhythmic quantization on Symbolic Data.
Real-time Audio-to-Score Alignment.
This is a continuation of prior work of team-founder  which proved the utility of strongly-timed probabilistic models in form of Semi-Markov Hidden States. Our most important theoretical contribution is reported in ,  that introduced Time-coherency criteria for probabilistic models and led to general robustness of the Antescofo listening machine, and allowed its deployment for all music instruments and all setups around the world. We further studied the integration of other recognition algorithms in the algorithm in form of Information Fusion and for singing voice based on Lyric data in . Collaboration with our japanese counterparts led to extensions of our model to the symbolic domain reported in . Collaboration with the SIERRA team created a joint research momentum for fostering such applications to weakly-supervised discriminative models reported in . Our Real-time Audio-to-Score alignment is a major component of the Antescofo software described in Section 5.1.
Online Methods for Audio Segmentation and Clustering.
To extend our listening approach to general sound, we envisioned dropping the prior information provided by music scores and replacing it by the inherent structure in general audio signals. Early attempts by the team leader employed  Methods of Information Geometry, an attempt to join Information Theory, Differential Geometry and Signal Processing. We were among the first teams in the world advocating the use of such approaches for audio signal processing and we participated in the growth of the community. A major break-through of this approach is reported in  and the PhD Thesis  that outline a general real-time change detection mechanism. Automatic structure discovery was further pursued in a MS thesis project in 2013 . By that time we realized that Information Manifolds do not necessarily provide the invariance needed for automatic structure discovery of audio signals, especially for natural sounds. Following this report, we pursued an alternative approach in 2014 and in collaboration with the Inria SIERRA Team . The result of this joint work was published in IEEE ICASSP 2015 and won the best student paper award . We are currently studying massive applications of this approach to natural sounds and in robotics applications in the framework of Maxime Sirbu's PhD project.
Symbolic Music Information Retrieval and Rhythm Transcription.
Rhythmic data are commonly represented by tree structures (rhythms trees) due to the theoretical proximity of such structures with the proportional representation of time values in traditional musical notation. We are studying the application to rhythm notation of techniques and tools for symbolic processing of tree structures, in particular tree automata and term rewriting.
Our main contribution in that context is the development of a new framework for rhythm transcription , , ,  addressing the problem of converting a sequence of timestamped notes, e.g. a file in MIDI format, into a score in traditional music notation. This problem is crucial in the context assisted music composition environments and music score editors. It arises immediately as insoluble unequivocally: in order to fit the musical context, the system has to balance constraints of precision and readability of the generated scores. Our approach is based on algorithms for the exploration and lazy enumeration of large sets of weighted trees (tree series), representing possible solutions to a problem of transcription. A side problem concerns the equivalent notations of the same rhythm, for which we have developed a term rewrite approach, based on a new equational theory of rhythm notation , , .