I’m using this doc http://code.compartmental.net/minim/
Is it outdated ?
Anyway the following works. The second error was due to the play() function called in the setup().
Minim minim;
AudioPlayer player;
static final int FADE = 2500;
void setup() {
minim = new Minim(this);
player = minim.loadFile("walk.wav");
}
void draw() {
player.play();
player.shiftGain(player.getGain(),-80,FADE);
}