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Extract Voices from Music Signal

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Implement a basic digital music synthesizer and use it to play a traditional song in a three-voice arrangement. Specify a sample rate of 2 kHz. Save the song as a MATLAB® timetable.

fs = 2e3; t = 0:1/fs:0.3-1/fs; fq = [-Inf -9:2]/12; note = @(f,g) [1 1 1]*sin(2*pi*440*2.^[fq(g)-1 fq(g) fq(f)+1]'.*t); mel = [5 3 1 3 5 5 5 0 3 3 3 0 5 8 8 0 5 3 1 3 5 5 5 5 3 3 5 3 1]+1; acc = [5 0 8 0 5 0 5 5 3 0 3 3 5 0 8 8 5 0 8 0 5 5 5 0 3 3 5 0 1]+1; song = [];forkj = 1:length(mel) song = [song note(mel(kj),acc(kj)) zeros(1,0.01*fs)];endsong = song'/(max(abs(song))+0.1);% To hear, type sound(song,fs)调=时间表(歌曲,SampleRate = fs);

OpenSignal Analyzerand drag the timetable from theWorkspace Browserto the Signal table. ClickDisplay Gridto create a two-by-two grid of displays. Add a spectrum view to the top two displays and the lower left display. Select the lower right display, clickTime-Frequencyto add a spectrogram view, and clickTimeto remove the time view. Drag the song to all four displays. Select the lower right display, and on theSpectrogramtab, specify a time resolution of0.31second and0% overlap between adjoining segments. Set thePower Limitsto–50dB and–10dB.

Signal Analyzer window showing three copies of the waveform and spectrum of a music signal. A fourth display shows the spectrogram of the signal.

On theAnalyzertab, clickDuplicate创建三个副本的三倍e song. Rename the copies ashigh,medium, andlowby double-clicking theNamecolumn in the Signal table. Move the copies to the top two and lower left displays.

Select all three duplicate signals in the Signal table and clickPreprocessto enter the preprocessing mode.

  1. Select thehighsignal by clicking its name in the Signal table. SelectHighpassfrom theFunctionsgallery. In theFunction Parameterspanel, enter a passband frequency of450Hz and increase the steepness to0.95. ClickApply.

  2. Select themediumsignal by clicking its name in the Signal table. SelectBandpassfrom theFunctionsgallery. In theFunction Parameterspanel, enter230Hz and450Hz as the lower and upper passband frequencies, respectively. Increase the steepness to0.95. ClickApply.

  3. Select thelowsignal by clicking its name in the Signal table. SelectLowpassfrom theFunctionsgallery. In theFunction Parameterspanel, enter a passband frequency of230Hz and increase the steepness to0.95. ClickApply.

ClickAccept Allto save the preprocessing results and exit the mode.

Signal Analyzer window showing highpass-filtered, bandpass-filtered, and lowpass-filtered copies of a music signal

View a spectrogram on each of the three displays containing filtered signals.

  1. Remove the original signal by clearing the check box next to its name.

  2. On theDisplaytab, clickTime-Frequencyto add a spectrogram view and clickTimeto remove the time view.

  3. On theSpectrogramtab, specify a time resolution of0.31second and0% overlap between adjoining segments. Set thePower Limitsto–50dB and–10dB.

Signal Analyzer window showing the three voices in a music signal

Select the three filtered signals by clicking theirNamecolumn in the Signal table. On theAnalyzertab, clickExportand save the signals to a MAT-file calledmusic.mat. In MATLAB, load the file to the Workspace. Plot the spectra of the three signals.

loadmusicpspectrum(low) holdonpspectrum(medium) pspectrum(high) holdoff

Figure contains an axes object. The axes object with title Fres = 1.9536 Hz, xlabel Frequency (kHz), ylabel Power Spectrum (dB) contains 3 objects of type line.

% To hear the different voices, type% sound(low.low,fs), pause(5), sound(medium.medium,fs), pause(5), sound(high.high,fs)

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