I'd like to know how to initialize multiple frequencies.

Question

Hello 
 I would like to use three PWM to output multiple sounds with one buzzer. 
 First of all, I am testing using two PWM. There is no problem using only one PWM, but there seems to be a problem with the initialization when using two. 
 
 APP_PWM_INSTANCE(PWM1,1); // Create the instance "PWM1" using TIMER1 (name, NRF_DRV_TIMER_INSTANCE(num)).
APP_PWM_INSTANCE(PWM2,3); // Create the instance "PWM2" using TIMER2.

void pwm_play_buzzer_duration(uint32_t duration)
{
 uint8_t i;
 uint32_t duty = 50;

 NRF_LOG_INFO("pwm_play_buzzer_duration =>"); 
 ready_flag = false;

 //Set the duty cycle - keep trying until PWM is ready... 
 while (app_pwm_channel_duty_set(&PWM1, 0, duty) == NRF_ERROR_BUSY);

 nrf_delay_ms(duration);
 app_pwm_disable(&PWM1);
}

void pwm_play_buzzer_duration_2(uint32_t duration) 
{
 uint8_t i;
 uint32_t duty = 50;

 NRF_LOG_INFO("pwm_play_buzzer_duration =>"); 
 ready_flag = false;

 // Set the duty cycle - keep trying until PWM is ready... 
 while (app_pwm_channel_duty_set(&PWM2, 0, duty) == NRF_ERROR_BUSY);

 nrf_delay_ms(duration);
 app_pwm_disable(&PWM2);
}

void pwm_init(void) 
{
 ret_code_t err_code;

 /* 1-channel PWM, 200Hz, output on DK LED pins. */
 app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(1500, BUZZER_PIN); //original 5000L
 
 /* Switch the polarity of the second channel. */
 pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
 
 /* Initialize and enable PWM. */
 err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
 APP_ERROR_CHECK(err_code);
 app_pwm_enable(&PWM1);


 app_pwm_config_t pwm2_cfg = APP_PWM_DEFAULT_CONFIG_1CH(5000, BUZZER_PIN); 
 
 pwm2_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;
 
 err_code = app_pwm_init(&PWM2,&pwm2_cfg,pwm_ready_callback);
 APP_ERROR_CHECK(err_code);
 app_pwm_enable(&PWM2);
}
 
 How should I set it up when I use multiple PWMs? 
 Thank you in advance.