Automatic Sample Detection in Polyphonic Music

by Siddharth Gururani

The term ‘sampling’ refers to the reuse of audio snippets from pre-existing digital recordings with appropriate modifications in new compositions in a way that it fits the musical context. Influential artists that have been sampled frequently by younger artists include, for example, James Brown, Stevie Wonder, and Michael Jackson. Since sampling is an important approach in at least some music genres, there are websites dedicated to linking samples to songs such as The annotation, however, is done manually by fans and
music aficionados. A system that can automatically detect sampling can help automate this process and could also be used in large scale musicological studies of artist influence across time and geographical space.

The task of automatic sample detection has not been explored in much detail. Some papers proposed methods involving a modified audio fingerprinting method and Non-negative Matrix Factorization (NMF). The block diagram below gives a broad overview of the method used in this work.

flowchart of the sample detection process

The algorithm we present also utilizes NMF and adds a post-processing step with subsequence Dynamic Time Warping (DTW) to extract features that indicate a sample/song pair. The figure below shows a distance matrix for a song in which the sample is looped 4 times in 20 seconds as indicated by the diagonal lines. We extract features from the detected paths and use them to train a random forest classifier.

distance matrix showing 4 repetitions of the looped sample

A new dataset had to be created for the evaluation of the system as previous publications lack systematic evaluation. This dataset originates from and is now publicly available. Our evaluation results, presented in the paper, indicate that our algorithm is has reasonably high precision while suffering from low recall which may be attributed to absence of clear alignment paths in the distance matrix.

For details on the method, results and discussion, please refer to the published paper available here.

Mixing Secrets: A Multi-Track Dataset for Instrument Recognition

by Siddharth Gururani

Instrument recognition as a task in Music Information Retrieval has had a long history and several datasets have been introduced for public use. The RWC dataset and the UIOWA dataset, for instance, are standard datasets for evaluation of instrument recognition in monophonic audio. The IRMAS dataset is a large dataset for predominant instrument detection. There are however, not many datasets available for instrument detection in polyphonic mixtures.

Muti-track data comes in handy for such a task. Multi-track datasets contain the recording sessions of songs, which will normally include the raw tracks, the stems, and the final mix. This enables the usage of multi-track datasets for a variety of tasks such as source separation and multi-f0 tracking, but also instrument recognition.

MedleyDB is a widely known dataset that contains 250 multi-tracks with a well defined annotation format and instrument taxonomy. While this might be considered an overwhelming amount of data, new data-hungry algorithms such as deep neural networks are often in need of more data for training and testing. We release a new set of annotated multi-track data in a format that is compatible to MedleyDB. It contains 258 multi-tracks originating from the website for a book titled “Mixing Secrets For the Small Studio.”

The paper contains more details about how the data was cleaned and processed in order to make it consistent with MedleyDB’s annotations. The github repository contains the code and links to the data.

Objective descriptors for the assessment of student music performances

by Amruta Vidwans

Learning a musical instrument is difficult. It needs regular practice, expert advice, and supervision. Even today, musical training is largely driven by interaction between student and a human teacher plus individual practice session at home.

Can technology improve this process and the learning experience? Can an algorithm perform an assessment of a student music performance? If yes, we are one step closer to a truly musically intelligent music tutoring system  that will support students learn their instrument of choice by providing feedback on aspects like rhythmic correctness, note accuracy, etc. An automatic assessment is not only useful to students for their practice sessions but could also help band directors in the auditioning and (pre-)selection process. While there are a few commercial products for practicing instruments, the assessment in these products is usually either trivial or opaque to the user.

The realization of a musically intelligent system for music performance assessment requires knowledge from multiple disciplines such as digital signal processing, machine learning, audio content analysis, musicology, and music psychology. With recent advances in Music Information Retrieval (MIR), noticeable progress has been made in related research topics.

Despite these efforts, identifying a reliable and effective method for assessing music performances remains an unsolved problem. In our study, we explore the effectiveness of various objective descriptors by comparing three sets of features extracted from the audio recording of a music performance, (i) a baseline set with common low-level features (often used but hardly meaningful for this task), (ii) a score-independent set with designed performance features (custom-designed descriptors such as pitch deviation etc., but without knowledge of the musical score), and (iii) a score-based set with designed performance features (taking advantage of the known musical score). The goal is to identify a set of meaningful objective descriptors for the general assessment of student music performances. The data we used covers Alto Saxophone recordings of three years of student auditions (Florida state auditions) rated by experts in the assessment categories of musicality, note accuracy, rhythmic accuracy, and tone quality.

Label: Musicality E1 E2 E3 E4
Correlation (r) 0.19 0.49 0.56 0.58

Our observations (as seen in Table 1) are that, as expected, the baseline features (E1) are not able to capture any qualitative aspects of the music performance so that the regression model mostly fails to predict the expert assessments . Another expected result is that score-based features (E3) are able represent the data generally better than score-independent features (E2) in all categories. The combination of score-independent and score-based features (E4) show some trend to improve results, but the gain remains small, hinting at redundancies between the feature sets. With values between 0.5 and 0.65 for the correlation between the prediction and the human assessments, there is still a long way to go before computers will be able to reliably assess student music performance, but the results show that an automatic assessment is possible to a certain degree.

To learn more, please see the published paper for details.

Header image used with kind permission of Rachel Maness from


It was great to see alumni and current students meet at the International Society for Music Information Retrieval Conference (ISMIR) in Suzhou, China.

Contributions from the group at the conference:




The Georgia Tech Center for Music Technology (GTCMT) has shown strong presence at the International Conference for Music Information Retrieval (ISMIR) with students, post-docs, and alumni.

Contributions from the group at the conference: