polyphonic ring tone generator

hi
can anyone suggest how to produce a Pulse Width Modulated single sine wave using direct digital synthesis technique which is to be used to produce the ring tone generator in a mobile phone in MATLAB???

the behaviour software is as follows:
Reset: NoteNumber=0;
NoteDurattion;

DrivingFrequencyhaseAccunulator=(PhaseAccumulator+Ton[NoteNumber].Pitch)
mod PhaseAccumulatorSize;
if((Tunelength=NoteNumber)&!Continous)
Stop
Elseif NoteDuration=Tune[NoteNumber].LengthofNote then
NoteDuration=0;
NoteNumber=NoteNumber+1;
Else
Output=Wavetable[PhaseAccumulator];
NoteDuration=NoteDuration+1;

thanks