Pitch Detection and Rhythm Recognition

1
Pitch Detection and Rhythm Recognition

• Presented by
• Brenda Bonderud
• January 24, 2006

2
Some Background

• Machine analysis fairly recent area of study with
  no single standard approach standing out above
  others.
• New methods being explored include neural nets.

3
History

• Man has always wanted to make sense of music.
• Ancient shruti scale
• Pythagorus' string
• Greek modes
• Galileo and Mersenne
• Tuning fork
• Measuring pitch, Savart's Disk
• Measuring intensity of sound

4
History

• Early images of sound
• modulating bunsen burners-manometric flames
• Singing flames and naked flames
• Sound modulated smoke
• High pressure water jets
• Wheatstone Kaleidophone
• Lissajous patterns
• Phonautograph
• Phonodeik

5
History

• Early Sound Recorders
• Edison's phonograph
• Gramophone
• Telegraphone
• Magnetophone

6
Pitch Recognition and Rhythm Recognition

• Two starting points
• In MIDI
• All information for events already generated in a
  MIDI note message.
• In raw sound waveform
• My focus for today

7
The PD Problem

• Applications
• Interactive Composition
• Accompainement
• Sound transformation
• Difficulties
• Attack Transients
• Low Frequencies
• High Frequencies
• Myopic Pitch Tracking
• Acoustical Ambience

8
PD Methods

• Time-domain Fundamental Period PD
• AutoCorrelation
• Adaptive Filter
• Frequency Domain
• Models of Human Ear

9
PD Methods

• Time Domain
• Zero Crossing
• Electro glottograpy or laryngograph
• AutoCorrelation
• AutoCorrelation compares copies of itself
• CrossCorrelation compares two seperate signals
• Adaptive Filters
• Narrow bandpass filter/difference detector
• Optimum Comb Method

10
PD Methods

• Frequency-domain PDs
• Tracking Phase Vocoder
• Cepstrum Analysis
• Models of Human Ear
• Three submodels
• Polyphonic Pitch Detection
• Analysis

11
Rhythm Recognition

• Applications
• Accompaniests
• Tempo Trackers
• Transcription
• Levels of Rhythm Recognition
• Low Event Detection
• Middle Transcription
• High Style Analysis

12
Levels of Rhythm Recognition

• Event Detection
• Amplitude Thresholding
• Separating Voices in Polyphonic Music
• Transcription
• Tempo Tracking
• Note Duration Assignment
• Grouping into Patterns
• Estimating Meter and Measure Boundaries
• Recovery

13
Personal Observations

• Some rhythm recognition analysis of my own
• How humans recognize rhythm or
• Let's run a mile in my iPod