View source for 356-winter-2026/hw2

= Programming Project #2: "Featured Artist" =
[https://ccrma.stanford.edu/courses/356-winter-2026/ Music and AI (Music356/CS470)] | Winter 2026 | Prof. Ge Wang

In this programming project, we will learn to work with '''audio features''' for both supervised and unsupervised tasks. These include a '''real-time genre-classifier''' and a '''feature-based audio mosaic tool'''. Using the latter, create a feature-based '''musical statement or performance'''!

=== Due Dates ===
* Milestone (Phase One complete + Phase Two prototype): '''webpage due Monday (2/2, 11:59pm) | in-class critique Tuesday (2/3)'''
* Final Deliverable: '''webpage due Monday (2/9, 11:59pm)'''
* In-class Presentation: '''Tuesday (2/10)'''

=== Discord is Friend ===
* ''direct any questions, rumination, outputs/interesting mistakes to our class Discord''

=== Things to Think With ===
* read/skim the classic article [https://ccrma.stanford.edu/courses/356-winter-2023/readings/2002-ieee-genre.pdf "Musical Genre Classification of Audio Signals"] (Tzanetakis and Cook, 2002)
** don't worry about the details yet; first get a general sense what audio features and how they can be used

=== Tools to Play With ===
* get the latest [https://chuck.stanford.edu/release ChucK release] (1.5.5.7 or higher)
** '''all platforms''' for this project, you will be using the command line version of chuck.
* [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/ '''sample code for all phases'''] (including optional video starter code)

=== GTZAN Dataset ===
* next, you'll need to download [https://chuck.stanford.edu/chai/data/gtzan/ the GTZAN dataset]
** 1000 30-second music clips, labeled by humans into ten genre categories

=== Phase One: Extract, Classify, Validate ===
* understanding audio, audio features, FFT, feature extraction
* extract different sets of audio features from GTZAN dataset
* run real-time classifier using different feature sets
* run cross-validation to evaluate the quality of classifier based different features
* you can find [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify'''relevant code here''']
** start playing with these, and reading through these to get a sense of what the code is doing
** [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify/example-centroid.ck '''example-centroid.ck'''] -- a basic example of using ChucK's unit analyzer framework (things connected using the upchuck operator <code>=^</code>) to extract an audio feature:
*** generate an input (a 440hz sine wave) -- this can be any audio source, e.g., adc for the microphone
*** take a Fast Fourier Transform (FFT) on a frame of audio (size is determined by the FFT size)
*** using the output of FFT's analysis to compute the Spectral Centroid for that frame of audio
*** note how the ChucK timing is used to precisely control how often to do a frame of analysis
*** the <code>.upchuck()</code> is used to trigger an analysis, automatically cascading up the <code>=^</code>
** [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify/example-mfcc.ck '''example-mfcc.ck'''] -- this is like the previous example, but now we compute a multi-dimensional feature, Mel Frequency Cepstral Coefficients (MFCCs)
** [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify/feature-extract.ck '''feature-extract.ck'''] -- in a "real-world" scenario, we would extract multiple features. a <code>FeatureCollector</code> is used to aggregate multiple features into a single vector (see comments in the file for more details)
** [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify/genre-classify.ck '''genre-classify.ck'''] -- using output of <code>feature-extract.ck</code>, do real-time classification by performing the same feature extraction and using k-NN to predict likelihood of each genre category (see comments in the file for more details)
** [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-1-classify/x-validate.ck '''x-validate.ck'''] -- using output of <code>feature-extract.ck</code>, do cross-validation to get a sense of the classifier quality
* experiment by choosing different features and different number of features, extracting them on GTZAN, try the real-time classifier, and perform cross-validation
** available features: Centroid, Flux, RMS, RollOff, ZeroX, MFCCs, Chroma, Kurtosis
** try at least '''five''' different feature configurations and evaluate the resulting classifier using cross-validation
*** keep in mind that the baseline score is .1 (a random classifier for 10 genre), and 1 is max
*** how do different--and different numbers of--features affect the classification results?
*** in your experiment, what configuration yielded the highest score in cross-validation? 
* briefly report on your experiments

=== Phase Two: Designing an Audio Mosaic Tool ===
* you can find phase 2 [https://ccrma.stanford.edu/courses/356-winter-2026/code/featured-artist/phase-2-mosaic/'''sample code here''']
* using what you've learned, build a database mapping sound frames (100::ms to 1::second) <=> feature vectors
** curate your own set of audio files can be mixture of
*** songs or song snippets; we will perform feature extraction on audio windows from beginning to end; in essence each audio window is a short sound fragment with its own feature vector)
*** (optional) short sound effects (~1 second), you may wish to extract a single vector per sound effect
** use/modify/adapt the <code>feature-extract.ck</code> code from Phase One to build your database of sound frames to feature vectors:
*** instead of generating one feature vector for the entire file, output a trajectory of audio windows and associated feature vectors
*** instead of outputting labels (e.g., "blues", "disco", etc.), output information to identify each audio window (e.g., filename and windowStartTime)
*** see reference implementation <code>mosaic-extract.ck</code>
** note this does not require any labels, and like word2vec, we want to situate each sound window in a N-dimension feature space
* play with <code>mosaic-similar.ck</code>: a feature-based sound explorer to query your database and perform similarity retrieval (using KNN2)
* using your database and retrieval tool and [https://en.wikipedia.org/wiki/Concatenative_synthesis concatenative synthesis] and the <code>mosaic-synth-mic.ck</code> and <code>mosaic-synth-doh.ck</code>, design an interactive audio mosaic generator
** feature-based
** real-time
** takes any audio input (mic or any unit generator)
** can be used for expressive audio mosaic creation
* there are many functionalities you can choose to incorporate into your mosaic synthesizer
** using a keyboard or mouse control to affect mosaic parameters: synthesis window length, pitch shift (through SndBuf.rate), selecting subsets of sounds to use, etc.
** a key to making this expressive is to try different sound sources; play with them A LOT, gain understanding of the code and experiment!
* (optional) do this in the audiovisual domain
** (idea) build a audiovisual mosaic instrument or music creation tool / toy
** (idea) build a GUI for exploring sounds by similarity; will need to reduce dimensions (using PCA or another technique) to 3 or 2 in order to visualize
** checkout [https://chuck.stanford.edu/chugl/examples/basic/video.ck '''ChuGL video example''']

=== Phase Three: Make a Musical Mosaic! ===
** use your prototype from Phase Two to create a feature-based musical mosaic in the form of a musical statement or performance
** (optional) do this in the audiovisual domain (e.g., with [https://chuck.stanford.edu/chugl ChuGL])

=== Reflections ===
* write ~300 words of reflection on your project. It can be about your process, or the product. What were the limitations (and how did you try to get around them?)

=== Milestone Deliverables ===
submit a webpage for the project so far, containing:
* a brief report of what you did / try / observed in Phase One, and a brief description of your experiments on in Phase Two so far
* a demo video (doesn't have to be polished) briefly documenting your experiments/adventures in Phase Two, and a very preliminary sketch of Phase Three (a creative statement or performance using your system)
* code and feature and usage instructions needed to run your system
* list and acknowledge the source material (audio and any video) and people who have helped you along the way; source audio/video do not need to be posted (can submit these privately in Canvas)
* In class, we will view your webpage/demo video and give one another feedback for this milestone.

=== Final Deliverables ===
* create a CCRMA webpage for this etude
** the URL should live at https://ccrma.stanford.edu/~YOURUSERID/356/hw2 or https://ccrma.stanford.edu/~YOURUSERID/470/hw2
** alternately, you may use Medium or another publishing platform (but please still link to that page from your CCRMA webpage)
* your webpage is to include
** a title and description of your project (free free to link to this wiki page)
** all relevant chuck code from all three phases
*** phase 1: all code used (extraction, classification, validation)
*** phase 2: your mosaic generator
*** phase 3: code used for your musical statement
** video recording of your musical statement (please start early!)
** your 300-word reflection
** any acknowledgements (people, code, or other things that helped you through this)
* submit to Canvas '''only your webpage URL'''