Paper Archive

This paper describes the use of Non-negative Tensor Factorisation models for the separation of drums from polyphonic audio. Improved separation of the drums is achieved through the incorporation of Gamma Chain priors into the Non-negative Tensor Factorisation framework. In contrast to many previous approaches, the method used in this paper requires little or no pre-training or use of drum templates. The utility of the technique is shown on real-world audio examples.

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This paper describes a sound synthesis technique that modulates the coefficients of allpass filter chains using audio-rate frequencies. It was found that modulating a single allpass filter section produces a feedback AM–like spectrum, and that its bandwidth is extended and further processed by non-sinusoidal FM when the sections are cascaded. The cascade length parameter provides dynamic bandwidth control to prevent upper range aliasing artifacts, and the amount of spectral content within that band can be controlled using a modulation index parameter. The technique is capable of synthesizing rich and evolving timbres, including those resembling classic virtual analog waveforms. It can also be used as an audio effect with pitch-tracked input sources. Software and sound examples are available at http://www.acoustics.hut.fi/publications/papers/dafx09-cm/

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This paper presents an approach to the synthesis of acoustic emission due to liquids in motion. First, the models for the liquid motion description, based on a particle-based fluid dynamics representation, and for the acoustic emission are described, along with the criteria for the control of the audio algorithms through the parameters of the particles system. Then, the experimental results are discussed for a configuration representing the falling of a liquid volume into an underlying rigid container.

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A system that tries to analyze polyphonic musical recordings of bowed-string instruments, extract synthesis parameters of individual instrument and then re-synthesize is proposed. In the analysis part, multiple F0s estimation and partials tracking are performed based on modified WGCDV (weighted greatest common divisor and vote) method and high-order HMM. Then, dynamic time warping algorithm is employed to align the above results with the score to improve the accuracy of the extracted parameters. In the re-synthesis part, simple additive synthesis is employed. Here, one can experiment on changing timbres, pitches and so on or adding vibrato or other effects on the same piece of music.

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The rich spectra of classic waveforms (sawtooth, square and triangular) are obtained by discontinuities in the waveforms or their derivatives. At the same time, the discontinuities lead to aliasing when the waveforms are digitally generated. To remove or reduce the aliasing, researchers have proposed various methods, mostly based on limiting bandwidth or smoothing the waveforms. This paper introduces a new approach to generate the virtual analog oscillators with no aliasing. The approach relies on generating an impulse train using a feedback delay loop, often used for the physical modeling of musical instruments. Classic waveforms are then derived from the impulse train with a leaky integrator. Although the output generated by this method is not exactly periodic, it perceptually sounds harmonic. While additional processing is required for time-varying pitch shifting, resulting in some high-frequency attenuation when the pitch changes, the proposed method is computationally more efficient than other algorithms and the high-frequency attenuation can be also adjusted.

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This paper deals with the problem of beat-tracking in an audiofile. Considering time-variable tempo and meter estimation as input, we study two beat-tracking approaches. The first one is based on an adaptation of a method used in speech processing for locating the Glottal Closure Instants. The results obtained with this first approach allow us to derive a set of requirements for a robust approach. This second approach is based on a probabilistic framework. In this approach the beat-tracking problem is formulated as an “inverse” Viterbi decoding problem in which we decode times over beat-numbers according to observation and transition probabilities. A beat-template is used to derive the observation probabilities from the signal. For this task, we propose the use of a machine-learning method, the Linear Discriminant Analysis, to estimate the most discriminative beat-template. We finally propose a set of measures to evaluate the performances of a beattracking algorithm and perform a large-scale evaluation of the two approaches on four different test-sets.

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In this paper we present a model for beat-synchronous analysis of musical audio signals. Introducing a real-time beat tracking model with performance comparable to offline techniques, we discuss its application to the analysis of musical performances segmented by beat. We discuss the various design choices for beat-synchronous analysis and their implications for real-time implementations before presenting some beat-synchronous harmonic analysis examples. We make available our beat tracker and beatsynchronous analysis techniques as externals for Max/MSP.

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We describe a novel Query-by-Example (QBE) approach in Music Information Retrieval, which allows a user to customize query examples by directly modifying the volume of different instrument parts. The underlying hypothesis is that the musical genre shifts (changes) in relation to the volume balance of different instruments. On the basis of this hypothesis, we aim to clarify the relationship between the change of the volume balance of a query and the shift in the musical genre of retrieved similar pieces, and thus help instruct a user in generating alternative queries without choosing other pieces. Our QBE system first separates all instrument parts from the audio signal of a piece with the help of its musical score, and then lets a user remix those parts to change acoustic features that represent musical mood of the piece. The distribution of those features is modeled by the Gaussian Mixture Model for each musical piece, and the Earth Movers Distance between mixtures of different pieces is used as the degree of their mood similarity. Experimental results showed that the shift was actually caused by the volume change of vocal, guitar, and drums.

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The suitability of optimal path finding methods for vocal melody extraction in polyphonic music is well recognized since they combine local pitch strength and temporal smoothness considerations in a global sense. However, when such single-F0 tracking systems are applied to sound mixtures in which pitched accompaniment is of comparable strength to the singing voice, they suffer from irrecoverable degradations. In this study we investigate the use of an optimal path finding method that is allowed to dynamically track multiple F0 paths, specifically two, through the F0 candidate space. It is shown that when such a system is applied to typical polyphonic mixtures with vocal solo the melodic information is indeed retrieved. Audio examples are available at http://www.ee.iitb.ac.in/daplab/DualF0TrackingResults_DAFx

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This paper investigates numerical simulation of a string coupled transversely to a resonant body. Starting from a complete nite difference formulation, a second model is derived in which the body is represented in modal form. The main advantage of this hybrid form is that the body model is scalable, i.e. the computational complexity can be adjusted to the available processing power. Numerical results are calculated and discussed for simplied models in the form of string-string coupling and string-plate coupling.

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