Searching for tone() in the Arduino-ESP32 framework yields no results. The equivalent solution is to use the ledc driver (general PWM LED controller).
Also see ESP32 PWM with Arduino IDE (Analog Output) | Random Nerd Tutorials
Example code
// the number of the LED pin
const int ledPin = 16; // 16 corresponds to GPIO16
// setting PWM properties
const int freq = 5000;
const int ledChannel = 0;
const int resolution = 8;
void setup(){
// configure LED PWM functionalitites
ledcSetup(ledChannel, freq, resolution);
// attach the channel to the GPIO to be controlled
ledcAttachPin(ledPin, ledChannel);
//output a Middle C
ledcWriteTone(ledChannel, 261.626);
}
void loop(){
//wait 5 secs
delay(5000);
//disable tone
ledcWriteTone(ledChannel, 0);
}