MATH
21 B
Mathematics Math21b Spring 2009
Linear Algebra and Differential Equations
Exhibit: Linear algebra: autotune
Course Head: Oliver Knill
Office: SciCtr 434



Youtube Demo of Autotune I

Youtube Demo of Autotune II
Autotune is also called the "photoshop of Music". Instead of looking better", one can "sound better". In the mathematica project, you get a bit insight into the mechanism, but it does things only in a very primitive way: the bad frequencies are filtered out. The real autotune shifts the frequencies to the right place.


Here is a very primitive Mathematica version of autotune in Mathematica:
A=Import["test.wav"]; M=8000; S=A[[1,1,1]]; n=Length[S];
tunes=Floor[Table[440*2^(k/12),{k,-36,55}]];
filter=Table[If[MemberQ[tunes,k],1,0],{k,M}];
S1[l_]:=Table[S[[l*M+k]],{k,M}];
S2[l_]:=FourierDCT[filter*FourierDCT[S1[l],2],3];
S3=Flatten[Table[S2[l],{l,0,Floor[n/M]-1}]];
U=Sound[SampledSoundList[{S3,S3},44100]];
Export["s.wav",U,"Wav"];
Please send questions and comments to math21b@fas.harvard.edu
Math21b (Exam Group 1)| Oliver Knill | Spring 2009 | Department of Mathematics | Faculty of Art and Sciences | Harvard University