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  • 1.
    Elowsson, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Modeling Music: Studies of Music Transcription, Music Perception and Music Production2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation presents ten studies focusing on three important subfields of music information retrieval (MIR): music transcription (Part A), music perception (Part B), and music production (Part C).

    In Part A, systems capable of transcribing rhythm and polyphonic pitch are described. The first two publications present methods for tempo estimation and beat tracking. A method is developed for computing the most salient periodicity (the “cepstroid”), and the computed cepstroid is used to guide the machine learning processing. The polyphonic pitch tracking system uses novel pitch-invariant and tone-shift-invariant processing techniques. Furthermore, the neural flux is introduced – a latent feature for onset and offset detection. The transcription systems use a layered learning technique with separate intermediate networks of varying depth.  Important music concepts are used as intermediate targets to create a processing chain with high generalization. State-of-the-art performance is reported for all tasks.

    Part B is devoted to perceptual features of music, which can be used as intermediate targets or as parameters for exploring fundamental music perception mechanisms. Systems are proposed that can predict the perceived speed and performed dynamics of an audio file with high accuracy, using the average ratings from around 20 listeners as ground truths. In Part C, aspects related to music production are explored. The first paper analyzes long-term average spectrum (LTAS) in popular music. A compact equation is derived to describe the mean LTAS of a large dataset, and the variation is visualized. Further analysis shows that the level of the percussion is an important factor for LTAS. The second paper examines songwriting and composition through the development of an algorithmic composer of popular music. Various factors relevant for writing good compositions are encoded, and a listening test employed that shows the validity of the proposed methods.

    The dissertation is concluded by Part D - Looking Back and Ahead, which acts as a discussion and provides a road-map for future work. The first paper discusses the deep layered learning (DLL) technique, outlining concepts and pointing out a direction for future MIR implementations. It is suggested that DLL can help generalization by enforcing the validity of intermediate representations, and by letting the inferred representations establish disentangled structures supporting high-level invariant processing. The second paper proposes an architecture for tempo-invariant processing of rhythm with convolutional neural networks. Log-frequency representations of rhythm-related activations are suggested at the main stage of processing. Methods relying on magnitude, relative phase, and raw phase information are described for a wide variety of rhythm processing tasks.

  • 2.
    Elowsson, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Polyphonic Pitch Tracking with Deep Layered LearningManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a polyphonic pitch tracking system able to extract both framewise and note-based estimates from audio. The system uses six artificial neural networks in a deep layered learning setup. First, cascading networks are applied to a spectrogram for framewise fundamental frequency (f0) estimation. A sparse receptive field is learned by the first network and then used for weight-sharing throughout the system. The f0 activations are connected across time to extract pitch ridges. These ridges define a framework, within which subsequent networks perform tone-shift-invariant onset and offset detection. The networks convolve the pitch ridges across time, using as input, e.g., variations of latent representations from the f0 estimation networks, defined as the “neural flux.” Finally, incorrect tentative notes are removed one by one in an iterative procedure that allows a network to classify notes within an accurate context. The system was evaluated on four public test sets: MAPS, Bach10, TRIOS, and the MIREX Woodwind quintet, and performed state-of-the-art results for all four datasets. It performs well across all subtasks: f0, pitched onset, and pitched offset tracking.

  • 3.
    Elowsson, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Tempo-Invariant Processing of Rhythm with Convolutional Neural NetworksManuscript (preprint) (Other academic)
    Abstract [en]

    Rhythm patterns can be performed with a wide variation of tempi. This presents a challenge for many music information retrieval (MIR) systems; ideally, perceptually similar rhythms should be represented and processed similarly, regardless of the specific tempo at which they were performed. Several recent systems for tempo estimation, beat tracking, and downbeat tracking have therefore sought to process rhythm in a tempo-invariant way, often by sampling input vectors according to a precomputed pulse level. This paper describes how a log-frequency representation of rhythm-related activations instead can promote tempo invariance when processed with convolutional neural networks. The strategy incorporates invariance at a fundamental level and can be useful for most tasks related to rhythm processing. Different methods are described, relying on magnitude, phase relationships of different rhythm channels, as well as raw phase information. Several variations are explored to provide direction for future implementations.

  • 4.
    Lã, Filipa M.B.
    et al.
    University of Distance-Learning, MADRID, Spain.
    Ternström, Sten
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Speech, Music and Hearing, TMH, Music Acoustics.
    Flow ball-assisted training: immediate effects on vocal fold contacting2019In: Pan-European Voice Conference 2019 / [ed] Jenny Iwarsson, Stine Løvind Thorsen, University of Copenhagen , 2019, p. 50-51Conference paper (Refereed)
    Abstract [en]

    Background: The flow ball is a device that creates a static backpressure in the vocal tract while providing real-time visual feedback of airflow. A ball height of 0 to 10 cm corresponds to airflows of 0.2 to 0.4. L/s. These high airflows with low transglottal pressure correspond to low flow resistances, similar to the ones obtained when phonating into straws with 3.7 mm diameter and of 2.8 cm length. Objectives: To investigate whether there are immediate effects of flow ball-assisted training on vocal fold contact. Methods: Ten singers (five males and five females) performed a messa di voce at different pitches over one octave in three different conditions: before, during and after phonating with a flow ball. For all conditions, both audio and electrolaryngographic (ELG) signals were simultaneously recorded using a Laryngograph microprocessor. The vocal fold contact quotient Qci (the area under the normalized EGG cycle) and dEGGmaxN (the normalized maximum rate of change of vocal fold contact area) were obtained for all EGG cycles, using the FonaDyn system. We introduce also a compound metric Ic ,the ‘index of contact’ [Qci × log10(dEGGmaxN)], with the properties that it goes to zero at no contact. It combines information from both Qci and dEGGmaxN and thus it is comparable across subjects. The intra-subject means of all three metrics were computed and visualized by colour-coding over the fo-SPL plane, in cells of 1 semitone × 1 dB. Results: Overall, the use of flow ball-assisted phonation had a small yet significant effect on overall vocal fold contact across the whole messa di voce exercise. Larger effects were evident locally, i.e., in parts of the voice range. Comparing the pre-post flow-ball conditions, there were differences in Qci and/or dEGGmaxN. These differences were generally larger in male than in female voices. Ic typically decreased after flow ball use, for males but not for females. Conclusion: Flow ball-assisted training seems to modify vocal fold contacting gestures, especially in male singers.

  • 5.
    Pabon, Peter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics. Royal Conservatoire, The Hague, Netherlands.
    Ternström, Sten
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Feature maps of the acoustic spectrum of the voice2018In: Journal of Voice, ISSN 0892-1997, E-ISSN 1873-4588Article in journal (Refereed)
    Abstract [en]

    The change in the spectrum of sustained /a/ vowels was mapped over the voice range from low to high fundamentalfrequency and low to high sound pressure level (SPL), in the form of the so-called voice range profile (VRP). In eachinterval of one semitone and one decibel, narrowband spectra were averaged both within and across subjects. Thesubjects were groups of 7 male and 12 female singing students, as well as a group of 16 untrained female voices. Foreach individual and also for each group, pairs of VRP recordings were made, with stringent separation of themodal/chest and falsetto/head registers. Maps are presented of eight scalar metrics, each of which was chosen toquantify a particular feature of the voice spectrum, over fundamental frequency and SPL. Metrics 1 and 2 chart the roleof the fundamental in relation to the rest of the spectrum. Metrics 3 and 4 are used to explore the role of resonances inrelation to SPL. Metrics 5 and 6 address the distribution of high frequency energy, while metrics 7 and 8 seek todescribe the distribution of energy at the low end of the voice spectrum. Several examples are observed ofphenomena that are difficult to predict from linear source-filter theory, and of the voice source being less uniform overthe voice range than is conventionally assumed. These include a high-frequency band-limiting at high SPL and anunexpected persistence of the second harmonic at low SPL. The two voice registers give rise to clearly different maps.Only a few effects of training were observed, in the low frequency end below 2 kHz. The results are of potentialinterest in voice analysis, voice synthesis and for new insights into the voice production mechanism.

  • 6. Rossing, T D
    et al.
    Sundberg, Johan
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Ternström, Sten
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Acoustic comparison of soprano solo and choir singing.1987In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 82, no 3, p. 830-836Article in journal (Refereed)
    Abstract [en]

    Five soprano singers were recorded while singing similar texts in both choir and solo modes of performance. A comparison of long-term-average spectra of similar passages in both modes indicates that subjects used different tactics to achieve somewhat higher concentrations of energy in the 2- to 4-kHz range when singing in the solo mode. It is likely that this effect resulted, at least in part, from a slight change of the voice source from choir to solo singing. The subjects used slightly more vibrato when singing in the solo mode.

  • 7. Rossing, T D
    et al.
    Sundberg, Johan
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Ternström, Sten
    Acoustic comparison of voice use in solo and choir singing.1986In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 79, no 6, p. 1975-1981Article in journal (Refereed)
    Abstract [en]

    An experiment was carried out in which eight bass/baritone singers were recorded while singing in both choral and solo modes. Together with their own voice, they heard the sound of the rest of the choir and a piano accompaniment, respectively. The recordings were analyzed in several ways, including computation of long-time-average spectra for each passage, analysis of the sound levels in the frequency ranges corresponding to the fundamental and the "singer's formant," and a comparison of the sung levels with the levels heard by the singers. Matching pairs of vowels in the two modes were inverse filtered to determine the voice source spectra and formant frequencies for comparison. Differences in both phonation and articulation between the two modes were observed. Subjects generally sang with more power in the singer's formant region in the solo mode and with more power in the fundamental region in the choral mode. Most singers used a reduced frequency distance between the third and fifth formants for increasing the power in the singer's formant range, while the difference in the fundamental was mostly a voice source effect. In a choral singing mode, subjects usually adjusted their voice levels to the levels they heard from the other singers, whereas in a solo singing mode the level sung depended much less on the level of an accompaniment.

  • 8.
    Ternström, Sten
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Nordmark, Jan
    KTH, School of Electrical Engineering and Computer Science (EECS), Speech, Music and Hearing, TMH, Music Acoustics.
    Intonation preferences for major thirds with non-beating ensemble sounds1996In: Proc. of Nordic Acoustical Meeting: NAM'96, Helsinki, 1996, p. 359-365, article id F2Conference paper (Refereed)
    Abstract [en]

    The frequency ratios, or intervals, of the twelve-tone scale can be mathematically dejned in several slightly diferent ways, each of which may be more or less appropriate in different musical contexts. For maximum mobility in musical key, instruments of our time with fixed tuning are typically tuned in equal temperament, except for performances of early music or avant-garde contemporary music. Some contend that pure intonation, being free of beats, is more natural, and would be preferred in instruments with variable tuning. The sound of choirs is such that beats are very unlikely to serve as cues for intonation. Choral performers have access to variable tuning, yet have not been shown to prefer pure intonation. The difference between alternative intonation schemes is largest for the major third interval. Choral directors and other musically expert subjects were asked to adjust to their preference the intonation of 20 major third intervals in synthetic ensemble sounds. The preferred size of the major third was 395.4 cents, with intra-subject averages ranging from 388 to 407 cents.

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