digital audio and computer music cos 116: 2/26/2008
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Digital audio and computer music
COS 116: 2/26/2008
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Overview
1. Sound and music in the physical world and in human experience
2. Representations of music
3. Analyzing music with computers
4. Creating music with computers
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1. Sound and music
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What is sound?
Discussion Time
“Pressure wave”
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What do we hear?
Video: http://www.youtube.com/watch?v=0svoQcMQNYg
Frequency Pitch Loudness Timbre …
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Psychoacoustics Relationships between physical phenomenon of sound
and our perception Frequency : pitch
20-20,000Hz
Amplitude : loudness Identities and strengths of frequencies present : timbre
+ =
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Discussion Time
What is music?
“Organized sound”
• Psychoacoustics play an important role• Also dependence upon history, culture, experience• Engages listeners’ psychological mechanisms for expectation/reward
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2. Representations of sound and music
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Score:
Audio samples Spectrum
Discussion Time
How do you represent music?
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Digital representation of music
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Compression A “better” representation with fewer bits Why? Security, transmission, storage How?
Psychoacoustic principles MP3: Masking
Physical principles of sound production (uses modelsof sound source)
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Choosing a representation
Representations are compromises Standard representations are somewhat
arbitrary Appropriate representation is task-
dependent
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3. Using technology to analyze sound and music
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Analyzing speech
Real-life apps: Customer service phone routing Voice recognition software
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Computational Auditory Scene Analysis
Applications: Archival and retrieval, forensics, AI
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Music information retrieval
Analyzing musical data Query, recommend, visualize, transcribe,
detect plagiarism, follow along with a score
Sites you can trymidomi.comThemefinder.comPandora.com (human-driven), last.fm
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Machine learning for analysis
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4. Using technology to create music and soundA whirlwind tour of the 20th century, with a focus on computer technology
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Creating music: Synthesis
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Three approaches to synthesis
Additive synthesis1. Figure out which frequencies are present, and in
what proportions2. Synthesize a sine wave at each frequency, and
superpose them.
1. Physical modeling1. Start with knowledge about how physical systems
oscillate2. Simulate oscillation of an arbitrary system. (Recall
Lecture 4)
+ + …=
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Three approaches to synthesis Cross-synthesis
Choose filter for speech (vowel) Choose source to be another sound
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Some continua of computer music creation
Synthesis
Controlling synthesis
Composition
low
highLevel of control
Running a program
Computer follows performer
Live coding, special controllers
Interactivity
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Performer-Computer Interaction
Augmented instruments Software and hardware interfaces
Demo: PLOrk video, PBS Demo: using a Wii-mote to control sound Demo: SMELT
New instruments Demo: Perry’s Mug
Live coding Demo: Max’s drum machine
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Questions: How can we….
develop new ways to synthesize sound? give user control over synthesis parameters? make machines interactive in a musical way? augment human capabilities? design new instruments that are easy to play?
allow expert musicality? create music that is emotionally and
aesthetically compelling?
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Final remarks Distinctions in this presentation are superficial
Analysis, representation, and creation interact Technology draws on and contributes to our understanding of the
physics and psychophysics of sound Computer music is interdisciplinary
HCI, AI, programming languages, algorithms, systems building Also psychology, music theory, acoustics, signal processing,
engineering, physics, performance practice, library science, applied math & statistics, …
Technology is constantly complicating and changing the landscape of our musical experiences as creators, participants, listeners, and consumers.
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http://soundlab.cs.princeton.edu/
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