TinyChan

let mod=(n,m)=>(n%m+m)%m,
    read=(a,i)=>a[mod(Math.floor(i),a.length)],
    mix=(a,b,x)=>a+(b-a)*x,
    noteHz=n=>440*2**(n/12),
    rand=(...a)=>a.length===2?mix(a[0],a[1],Math.random()):a.length===1?Math.random()*x[0]:Math.random(),
    pow2=(x,y)=>Math.pow(Math.abs(x),y)*Math.sign(x);
class StringWave{
  constructor(N,damp=1.001,c=.2){
    this.N=N;this.heights=new Array(N);this.velocities=new Array(N);
    this.pluck(rand(),pow2(rand(-1,1),.3));
    this.damp=damp;this.c=c;
  }
  pluck(x,y){
    let xi=x*this.N;
    for(let i=0;i<this.N;i++){
      this.heights[i]=i<xi?y*(i/xi):y*(1-(i/xi)/(this.N-xi));
      this.velocities[i]=0;
    }
  }
  update(){
    const v=this.velocities,h=this.heights;
    for(let i=1;i<this.N-1;i++)
      v[i]=(v[i]+2*(h[i-1]+h[i+1]-2*h[i]))/this.damp;
    for(let i=0;i<this.N;i++)
      h[i]+=v[i]*this.c;
  }
}
function normalize(array){
  let mn=Math.min(...array),
      mx=Math.max(...array),
      o=[];
  if(mn===mx)return array;
  for(let i=0;i<array.length;i++)
    o[i]=mix(-1,1,(array[i]-mn)/(mx-mn));
  return o;
}
let SR=8000,
    N=70,chord=[0,3,7,10,14,15,17,22],w=[],a=[];
for(let i=0;i<8;i++){
  w[i]=new StringWave(N,1.0005,.29);
  a[i]=[];
  for(let j=0;j<SR*2.8;j++){
    w[i].update();
    a[i][j]=w[i].heights[floor(N*(.25+sin((j/SR)*3)*.2))];
  }
  a[i]=normalize(a[i]);
  //declicking
  let fade=128;
  for(let j=0;j<fade;j++){
    a[i][j]*=(j+1)/(fade+1);
    a[i][(a[i].length-1)-j]*=(j+1)/(fade+1);
  }
}


let samp=()=>{
  let t=0;
  return(si,sa)=>{
    t+=sa/32e3;
    let a0=read(a[mod(floor(si),a.length)],t),
        a1=read(a[mod(floor(si)+1,a.length)],t);
    return mix(a0,a1,mod(si,1));
  };
},s=chord.map(n=>[samp(),samp()]);
return t=>{
  let o=0;
  for(let i=0;i<chord.length;i++){
    //o+=read(a[mod(floor(i+t),a.length)],t*noteHz(chord[i])*N)-read(a[mod(floor(i+t*.5),a.length)],-t*noteHz(chord[i])*1.02*N);
    o+=s[i][0](t+i,noteHz(chord[i]+sin(t*7+i*.3)*.05)*N)-s[i][1](t+i*2,-noteHz(chord[i]+sin(t*6.5+i*.6)*.06)*N);
  }
  return tanh(o*.3);
};