1. Music Transcription through Statistical Analysis Group 3 Austin Assavavallop, William Feater, Greg Heim, Philipp Pfieffenberger, Wamba Yves Design Phase Presentation

2. Music Transcription Challenge: Decode note information from a monophonic music signal Overview of chosen approach –Noise vs. Signal –Pitch Detection –Timing Analysis –Note Detection Development and Implementation

3. Sound Waves to Tablature Sample stream into frames Identify events frame-by-frame Control a state machine with frame events State machine reports each note’s onset, velocity, pitch, and pauses.

4. What’s music, anyway? Notes –Time limited –Periodic –Audible frequencies –Random phase offset –Considerable* signal energy Rests –Not periodic –Relatively little* signal energy (noise) *Comparatively

5. Noise Characterization Notes vs. Rests –High signal energy: Note –Low signal energy: Rest How much energy is due to noise? –Assume system noise at start of operation –Calculate Mean, Standard Deviation Assume Gaussian noise –Mean ~ 0 –Expected Noise Amplitude =~ Std. Dev. Set threshold for pause –P(High Signal Energy | only noise) =~ 0 –Threshold ~= 3 * Std. Dev. of noise

6. Pitch Detection Pitch Detector Period N p Sample Frame s(n)

7. Pitch Detection Fundamental Period

8. Pitch Detection: A4

9. Pitch Detection Assume western scale –f A1 =55Hz, f A2 =110Hz,.. f AN =55*2 N –Determine frequency presence in signal Take advantage of period multiples Probe signal for all notes of first octave Probe multiples of closest note Fundamental = lowest harmonic period

10. Pitch Detection: Correlation s(n) : Sampled frame, N p = attempted period Caveat: Like all frequency detection techniques, correlation leads to a tradeoff between the lowest detectable frequency and timing accuracy.

11. Timing Analysis Pitch N p A V Sample Frame s(n) Amplitude Variance

12. Timing Analysis Detect frame’s fundamental frequency Divide frame into one period blocks Measure energy of each block

13. Timing Analysis Variance: Variance of block energies Frame Amplitude: Average block energy

14. Envelope Analysis System Overview Pitch Detector Frame s(n) = [0..N] Pitch Amplitude Variance Controller Start, End time Velocity Pitch N p A V

15. Controller Start, End time Velocity Pitch Pitch N p Amplitude AVariance V

16. Controller Logic InitializationNew NoteStable NoteRest ΔN p ΔA ΔN p || ΔV ΔA && ΔV ΔA ΔN p && ΔV ΔA Only accessible before the first Stable Note Report Event

17. Implementation Design Approach Modularization Time domain – Timing Analysis, Controller Frequency domain – Pitch Detection Testing and Integration Implementation issues Processing within 45.3ms Optimization using libraries GUI for note interpretation

18. Questions?