The above code is much more like sine speech.
I think I have fathomed out how you did it :
4 narrow band pass filters, (narrowness inversely proportional to “width”), modulated with 1KHz sinusoidal carrier.
I am attempting to digest the Nyquist manual, although it may take me some time.
[BTW with some values the above code seems to change the geographic accent of speech, e.g. South African, Australian].