float oscili(amp,si,farray,len,phs)      
float amp,si,*farray,*phs;
register len;
{
	register i =  *phs;        
        register k =  (i + 1) % len;  
	float frac = *phs  - i;      
	*phs += si;                 
	while(*phs >= len)
		*phs -= len;       
	return((*(farray+i) + (*(farray+k) - *(farray+i)) *
					   frac) * amp);
}