Guys i have stuck.
At void setup() i use SD.begin(4) to read a text file from Sd.
When the reading of Sd completes i want to play music from Sd card (SdPlay.setSDCSPin(4) but i have already set pin(4) for reading the text.
Anyone knows how to reset the pin4 and use it again for listening music from sd?

void setup() {
Serial.begin(9600);

//-------------------------------------------------------------------
Serial.print("Initializing SD card...");

  if (!SD.begin(4)) {
    Serial.println("initialization failed!");
    return;
  }
  Serial.println("initialization done.");
  myFile = SD.open("test.txt", FILE_WRITE);
  if (myFile) {
    Serial.print("Writing to test.txt...");
    myFile.println("testing 1, 2, 3.");
    myFile.close();
    Serial.println("done.");
  } else {
    Serial.println("error opening test.txt");
  }
  myFile = SD.open("test.txt");
  if (myFile) {
    Serial.println("test.txt:");
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    // close the file:
    myFile.close();
  } else {
    // if the file didn't open, print an error:
    Serial.println("error opening test.txt");
  }
//----------------------------------------------------------------------------------------------------------
SdPlay.setSDCSPin(4); //------>Here problem caused
}

 

You are not making sense.

Pin 4 is a digital pin.
It is also PWM pin.

So. When you want it to output "music", it will do it as a PWM signal?

 

Also.
Since you are only reading from the file, remove the code for writing the file.

 

Or.
Just just use Pin 9 and Pin 10 like they do over here: https://www.hackerspace-ffm.de/wiki/index.php?title=SimpleSDAudio

 

i use this schematic for my sd card:
cs pin cannot go to pin4 and 9 (for example) because it will create short circuit.

 

You are not making sense.

Pin 4 is a digital pin.
It is also PWM pin.

So. When you want it to output "music", it will do it as a PWM signal?

yes as pwm signal with variable duty cycle