audio.loop() not running when called out of an function other than loop()

[TomCraftMC]

When i call my function which only content is "audio.loop" out of the loop() function it all works.
Here the code:

#include "Arduino.h"
#include <WiFi.h>
#include <WebServer.h>
#include "Audio.h"
#include "SD.h"
#include "FS.h"
#include <ArduinoJson.h>

WebServer server(80);

String wifiSSID = "StartProtect#1851";
String wifipasswd = "p{t#z9m~RJr#n<JTK0kS";

#define I2S_DOUT      22
#define I2S_BCLK      26
#define I2S_LRC       25

Audio audio;


void playSound(){
  audio.loop();
}

void handleRoot(){
  //playSound();
  server.send(200, "text/html", "<h1>Root - v2</h1>");
}

void setup() {
  delay(1000);
  Serial.begin(115200);
  Serial.println("");
  Serial.println("Starte System Nezwerk (SSID = '" + wifiSSID + "')");
  WiFi.mode(WIFI_AP);
  WiFi.softAP(wifiSSID, wifipasswd);
  Serial.print("IP Adresse ");
  Serial.println(WiFi.softAPIP());
  SD.begin();
  audio.setPinout(I2S_BCLK, I2S_LRC, I2S_DOUT);
  audio.setVolume(21);
  audio.connecttoFS(SD, "/Bang.wav");

  server.on("/", handleRoot);
  server.begin();

  Serial.println("Setup completed");

}

void loop() {
  playSound();
  server.handleClient();
}

But When I call the same function out of an function which is not loop() (I've also tried other than the one shown below) it does not work
Here The code:

#include "Arduino.h"
#include <WiFi.h>
#include <WebServer.h>
#include "Audio.h"
#include "SD.h"
#include "FS.h"
#include <ArduinoJson.h>

WebServer server(80);

String wifiSSID = "test";
String wifipasswd = "test";

#define I2S_DOUT      22
#define I2S_BCLK      26
#define I2S_LRC       25

Audio audio;


void playSound(){
  audio.loop();
}

void handleRoot(){
  playSound();
  server.send(200, "text/html", "<h1>Root - v2</h1>");
}

void setup() {
  delay(1000);
  Serial.begin(115200);
  Serial.println("");
  Serial.println("Starte System Nezwerk (SSID = '" + wifiSSID + "')");
  WiFi.mode(WIFI_AP);
  WiFi.softAP(wifiSSID, wifipasswd);
  Serial.print("IP Adresse ");
  Serial.println(WiFi.softAPIP());
  SD.begin();
  audio.setPinout(I2S_BCLK, I2S_LRC, I2S_DOUT);
  audio.setVolume(21);
  audio.connecttoFS(SD, "/Bang.wav");

  server.on("/", handleRoot);
  server.begin();

  Serial.println("Setup completed");

}

void loop() {
  server.handleClient();
}

[schreibfaul1]

In the simplest case, the audioI2S lib runs in the Arduino loop task and obtains the necessary computing time for the decoders from it. If you want it to be different, you can create your own task for the library.

[TomCraftMC]

Thanks, I've checked the code. The .loop() is [void Audio::loop()], isn't it?
But I haven't noticed anything that is excluding the function to be called out of other classes. Maybe you can give me a hint?