oneWave[f_, sampleRate_] :=
 Table[Cos[i 2 Pi], {i, 0, (f - 1)/f, f/sampleRate}]
nWaves[f_, sampleRate_, n_] :=
 Flatten[Table[oneWave[f, sampleRate], {i, 1, n}]]
ceg4 = ListPlay[a = nWaves[261.63`, 44100, 262];
  1/3 (a + Take[nWaves[329.63`, 44100, 330], Length[a]] +
     Take[nWaves[392.`, 44100, 392], Length[a]]), SampleRate -> 44100]

requencySplitDebug[signalList_List, splitF_?NumberQ, myDebugParams_List]:=
    Module[
        (* "Some common choices for {a,b} are {0,1} (default), {-1,1} (data analysis), {1,-1} (signal processing). " *)
        {signalLen, lfPart, hfPart, fourierData, myDebugGraphics, myDebugData, lfIF, hfIF, fourierA=0, fourierB=1,rPad, lPad},
        signalLen = Length[signalList];
        fourierData = Fourier[signalList, FourierParameters->{fourierA, fourierB}];
        rPad = PadRight[Take[fourierData,{1,splitF}],signalLen];
        lPad = PadLeft[Take[fourierData,{splitF + 1,signalLen}],signalLen];
        lfIF = InverseFourier[rPad,FourierParameters->{fourierA, fourierB}];
        hfIF = InverseFourier[lPad,FourierParameters->{fourierA, fourierB}];
        lfPart = Chop[Re[lfIF]];
        hfPart = Chop[Re[hfIF]];
        If[Length[myDebugParams]==3 && myDebugParams[[1]]==True && myDebugParams[[3]] > myDebugParams[[2]],
            Print["Debugging On"];
            myDebugGraphics =
                GraphicsGrid[{
                    {ListLinePlot[Take[signalList,{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All,PlotLabel->"Signal Input Detail"],
                    ListLinePlot[Take[Abs[fourierData],{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All, PlotLabel->"Signal Input Spectrum"]},
                    {ListLinePlot[Take[lfPart,{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All,PlotLabel->"Lower Part Signal Detail"],
                    ListLinePlot[Take[Abs[Fourier[lfPart,FourierParameters->{fourierA, fourierB}]],{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All, PlotLabel->"Lower Part Spectrum"]},
                    {ListLinePlot[Take[hfPart,{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All,PlotLabel->"Upper Part Signal Detail"],
                    ListLinePlot[Take[Abs[Fourier[hfPart,FourierParameters->{fourierA, fourierB}]],{myDebugParams[[2]],myDebugParams[[3]]}], PlotRange->All, PlotLabel->"Upper Part Spectrum"]}
                }];
            myDebugData = {fourierData, lfIF, hfIF};
        ];

        If[Length[myDebugData]==0,
            Return[{lfPart,hfPart}],
            Return[{lfPart,hfPart,myDebugGraphics, myDebugData}]
        ];
    ];

asplit = frequencySplitDebug[AudioData[ceg4], 300, {True, 1, 600}];
Show[asplit[[3]]]