Playing music with GP v3

START="start_aplay";
FREQ=8000;
A=440;
TEMPO=60/100*4;
CHANNEL=2;
start_aplay(fifo="/tmp/parififo")=
{
  system(Str("test -p ",fifo" || mkfifo ",fifo,"; aplay -r",FREQ," -q -traw -c",CHANNEL," < ",fifo," &"));
  fileopen(fifo,"w");
}
start_ffplay(fifo="/tmp/parififo")=
{
  system(Str("test -p ",fifo" || mkfifo ",fifo,"; ffplay -i pipe: -f u8 -ar ",FREQ," -ac ",CHANNEL," -hide_banner -autoexit -v 0 < ",fifo," &"));
  fileopen(fifo,"w");
}
start_ffplaygit() = fileextern(Str("ffplay -i pipe: -f u8 -ar ",FREQ," -ac ",CHANNEL," -hide_banner -autoexit -v 0"),"w");
start_aplaygit() = fileextern(Str("aplay -r",FREQ," -q -traw -c",CHANNEL),"w");

freq(n)= 2^(n/12)*A;

lerp(a,b,t) = a*(1-t)+b*t;

adsr(i,l,a,d,s,r) = 
{
  if(i<a, i/a,
     i<a+d, lerp(1,s,(i-a)/d),
     i>l-r, lerp(0,s,(l-i)/r),
     s);
}

playsound(f,freq,t,amp)=
{
  my(l=FREQ*TEMPO*t,a=FREQ*0.025,d=FREQ*0.05,s=0.66,r=FREQ*0.05);
  for(i=1,round(l), my(c=4*Pi*freq*i/FREQ);
     my(r=round(128+adsr(i,l,a,d,s,r)*(amp*besselj(0,c)*sqrt(c))));
     filewrite1(f,strchr(r));
     if (CHANNEL==1, next()); my(c=Pi*freq*i/FREQ);
     my(r=round(128+adsr(i,l,a,d,s,r)*(amp*besselj(Pi/2,c)*sqrt(c))));
     filewrite1(f,strchr(r));
  );
  print1(".");
  fileflush(f);
}

ode_to_joy="b4 b c' d' d' c' b a g g a b b4. a8 a2 b4 b c' d' d' c' b a g g a b a4. g8 g2 a4 a b g a b8 c' b4 g a b8 c' b4 a g a d2 b4 b c' d' d' c' b a g g a b a4. g8 g2";

la_marseillaise="r2 r8 r16 d16 d8. d16 g4 g a a d4. b8 g r16 g b8. g16 e4 c'2 a8. fis16 g2 r4 g8. a16 b4 b b c8. b16 b4 a r4 a8. b16 c4 c c d8. c16 b2 r4 d8. d16 d4 b8. g16 d'4 b8. g16 d2 r8 r16 d16 d8. fis16 a2 c4 a8. fis16 a4 g f2 e4 g8. g16 g4 fis8. g16 a2. r8 a8 bes4. bes8 bes bes c d a2. bes8 a g4. g8 g bes a g g4 fis8 r8 r4 r8 r16 d' d2 d8. d16 b8. g16 a2. r8 r16 d16 d2 d8. d16 b8. g16 a2 a8 r8 d,4 g2 r4 a4 b2 r2 c2 d4 e a,2 a8 r8 e'4 d2 d8. b16 c8. a16 g2. r4";
play(S,rl=0,rel)=
{
  my(mode=Map([0,0;1,2;2,3;3,5;4,7;5,9;6,10])); /*G major */
  my(f = call(eval(START),[]), T=4,d);
  foreach(strsplit(S," "), s,
    my(p=0,m=1,V=Vec(s),amp=120,nt=0,di=0);
    if (V[1]=="r",
       amp=0;
     , p=vecsearch(Vec("abcdefg"),V[1])-1;
       if (p<0,error(V));
       p=rel+centerlift(Mod(p-rel,7));
       );
    for(i=2,#V,
      my(c=V[i]);
      if(c=="i" && V[i+1]=="s",di++;i++
        ,c=="e" && V[i+1]=="s",di--;i++
        ,c=="'",p+=7
        ,c==",",p-=7
        ,c==".",m=3/2
        ,d=vecsearch(Vec("0123456789"),c), nt+=10*nt+d-1,
        ,error(V);
       ));
    if (nt,T = nt);
    if (amp,
      if(rl,rel = p);
      p = mapget(mode,p%7)+12*(p\7) + di);
    playsound(f,freq(p),m/T,amp));
  fileclose(f);
}
play(ode_to_joy,0,-2);
\\play(la_marseillaise,1,-7);