Android provides many ways to control playback of audio/video files and streams. One of this way is through a class called MediaPlayer.
Android is providing MediaPlayer class to access built-in mediaplayer services like playing audio,video e.t.c. In order to use MediaPlayer , we have to call a static Method create() of this class. This method returns an instance of MediaPlayer class. Its syntax is as follows:

MediaPlayer mediaPlayer = MediaPlayer.create(this, R.raw.song);

The second parameter is the name of the song that you want to play. You have to make a new folder under your project with name raw and place the music file into it.
Once you have created the Mediaplayer object you can call some methods to start or stop the music. These methods are listed below.

mediaPlayer.start();
mediaPlayer.pause();

On call to start() method, the music will start playing from the begininning. If this method is called again after the pause() method , the music would start playing from where it is left and not from the beginning.
In order to start music from the beginning , you have to call reset() method. Its syntax is given below.

mediaPlayer.reset();

Apart from the start and pause method , there are other methods provided by this class for better dealing with audio/video files. These methods are listed below:

Sr.No	Method & description
1	isPlaying() This method just returns true/false indicating the song is playing or not
2	seekTo(positon) This method takes an integer, and move song to that particular second
3	getCurrentDuration() This method returns the current position of song in milliseconds
4	getDuration() This method returns the total time duration of song in milliseconds
5	reset() This method resets the media player
6	release() This method releases any resource attached with MediaPlayer object
7	setVolume(float leftVolume, float rightVolume) This method sets the up down volume for this player
8	setDataSource(FileDescriptor fd) This method sets the data source of audio/video file
9	selectTrack(int index) This method takes an integer, and select the track from the list on that particular index
10	getTrackInfo() This method returns an array of track information

Example

Here is an example demonstrating the use of MediaPlayer class. It creates a basic media player that allows you to forwad , backward , play and pause a song.
To experiment with this example , you need to run this on an actual device to hear the audio sound.

Steps	Description
1	You will use Eclipse IDE to create an Android application and name it as MediaPlayer under a package com.example.mediaplayer. While creating this project, make sure you Target SDK and Compile With at the latest version of Android SDK to use higher levels of APIs.
2	Modify src/MainActivity.java file to add MediaPlayer code.
3	Modify the res/layout/activity_main to add respective XML components
4	Modify the res/values/string.xml to add necessary string components
5	Create a new folder under MediaPlayer with name as raw and place an mp3 music file in it with name as song.mp3
6	Run the application and choose a running android device and install the application on it and verify the results

Following is the content of the modifed main activity file src/com.example.mediaplayer/MainActivity.java.

package com.example.mediaplayer;

import java.util.concurrent.TimeUnit;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

   public TextView songName,startTimeField,endTimeField;
   private MediaPlayer mediaPlayer;
   private double startTime = 0;
   private double finalTime = 0;
   private Handler myHandler = new Handler();;
   private int forwardTime = 5000; 
   private int backwardTime = 5000;
   private SeekBar seekbar;
   private ImageButton playButton,pauseButton;
   public static int oneTimeOnly = 0;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      songName = (TextView)findViewById(R.id.textView4);
      startTimeField =(TextView)findViewById(R.id.textView1);
      endTimeField =(TextView)findViewById(R.id.textView2);
      seekbar = (SeekBar)findViewById(R.id.seekBar1);
      playButton = (ImageButton)findViewById(R.id.imageButton1);
      pauseButton = (ImageButton)findViewById(R.id.imageButton2);
      songName.setText("song.mp3");
      mediaPlayer = MediaPlayer.create(this, R.raw.song);
      seekbar.setClickable(false);
      pauseButton.setEnabled(false);

   }

   public void play(View view){
   Toast.makeText(getApplicationContext(), "Playing sound", 
   Toast.LENGTH_SHORT).show();
      mediaPlayer.start();
      finalTime = mediaPlayer.getDuration();
      startTime = mediaPlayer.getCurrentPosition();
      if(oneTimeOnly == 0){
         seekbar.setMax((int) finalTime);
         oneTimeOnly = 1;
      } 

      endTimeField.setText(String.format("%d min, %d sec", 
         TimeUnit.MILLISECONDS.toMinutes((long) finalTime),
         TimeUnit.MILLISECONDS.toSeconds((long) finalTime) - 
         TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
         toMinutes((long) finalTime)))
      );
      startTimeField.setText(String.format("%d min, %d sec", 
         TimeUnit.MILLISECONDS.toMinutes((long) startTime),
         TimeUnit.MILLISECONDS.toSeconds((long) startTime) - 
         TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
         toMinutes((long) startTime)))
      );
      seekbar.setProgress((int)startTime);
      myHandler.postDelayed(UpdateSongTime,100);
      pauseButton.setEnabled(true);
      playButton.setEnabled(false);
   }

   private Runnable UpdateSongTime = new Runnable() {
      public void run() {
         startTime = mediaPlayer.getCurrentPosition();
         startTimeField.setText(String.format("%d min, %d sec", 
            TimeUnit.MILLISECONDS.toMinutes((long) startTime),
            TimeUnit.MILLISECONDS.toSeconds((long) startTime) - 
            TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.
            toMinutes((long) startTime)))
         );
         seekbar.setProgress((int)startTime);
         myHandler.postDelayed(this, 100);
      }
   };
   public void pause(View view){
      Toast.makeText(getApplicationContext(), "Pausing sound", 
      Toast.LENGTH_SHORT).show();

      mediaPlayer.pause();
      pauseButton.setEnabled(false);
      playButton.setEnabled(true);
   } 
   public void forward(View view){
      int temp = (int)startTime;
      if((temp+forwardTime)<=finalTime){
         startTime = startTime + forwardTime;
         mediaPlayer.seekTo((int) startTime);
      }
      else{
         Toast.makeText(getApplicationContext(), 
         "Cannot jump forward 5 seconds", 
         Toast.LENGTH_SHORT).show();
      }

   }
   public void rewind(View view){
      int temp = (int)startTime;
      if((temp-backwardTime)>0){
         startTime = startTime - backwardTime;
         mediaPlayer.seekTo((int) startTime);
      }
      else{
         Toast.makeText(getApplicationContext(), 
         "Cannot jump backward 5 seconds",
         Toast.LENGTH_SHORT).show();
      }

   }

   @Override
   public boolean onCreateOptionsMenu(Menu menu) {
   // Inflate the menu; this adds items to the action bar if it is present.
   getMenuInflater().inflate(R.menu.main, menu);
   return true;
   }

 }

Following is the modified content of the xml res/layout/activity_main.xml.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:paddingBottom="@dimen/activity_vertical_margin"
   android:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   tools:context=".MainActivity" >

   <ImageButton
      android:id="@+id/imageButton3"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentBottom="true"
      android:layout_alignParentLeft="true"
      android:layout_marginBottom="14dp"
      android:onClick="forward"
      android:src="@android:drawable/ic_media_ff" />

   <ImageButton
      android:id="@+id/imageButton4"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentRight="true"
      android:layout_alignTop="@+id/imageButton2"
      android:layout_marginLeft="22dp"
      android:layout_toRightOf="@+id/imageButton2"
      android:onClick="rewind"
      android:src="@android:drawable/ic_media_rew" />

   <ImageButton
      android:id="@+id/imageButton2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignTop="@+id/imageButton1"
      android:layout_marginLeft="14dp"
      android:layout_toRightOf="@+id/imageButton1"
      android:onClick="pause"
      android:src="@android:drawable/ic_media_pause" />

   <ImageButton
      android:id="@+id/imageButton1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignTop="@+id/imageButton3"
      android:layout_marginLeft="24dp"
      android:layout_toRightOf="@+id/imageButton3"
      android:onClick="play"
      android:src="@android:drawable/ic_media_play" />

   <SeekBar
      android:id="@+id/seekBar1"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" 
      android:layout_above="@+id/imageButton3"
      android:layout_toLeftOf="@+id/textView2"
      android:layout_toRightOf="@+id/textView1" />

   <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignRight="@+id/imageButton3"
      android:layout_alignTop="@+id/seekBar1"
      android:text="@string/inital_Time"
      android:textAppearance="?android:attr/textAppearanceSmall" />

   <TextView
      android:id="@+id/textView2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignLeft="@+id/imageButton4"
      android:layout_alignTop="@+id/seekBar1"
      android:text="@string/inital_Time"
      android:textAppearance="?android:attr/textAppearanceSmall" />

   <TextView
      android:id="@+id/textView3"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignLeft="@+id/imageButton3"
      android:text="@string/hello_world"
      android:textAppearance="?android:attr/textAppearanceMedium" />

   <ImageView
      android:id="@+id/imageView1"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_alignParentBottom="true"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/textView3"
      android:src="@drawable/ic_launcher" />

   <TextView
      android:id="@+id/textView4"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignBaseline="@+id/textView3"
      android:layout_alignBottom="@+id/textView3"
      android:layout_toRightOf="@+id/imageButton1"
      android:text="TextView" />

</RelativeLayout>

Following is the content of the res/values/string.xml.

<?xml version="1.0" encoding="utf-8"?>
<resources>

   <string name="app_name">MediaPlayer</string>
   <string name="action_settings">Settings</string> 
   <string name="hello_world">Now Playing:</string>
   <string name="inital_Time">0 min, 0 sec</string>

</resources>

Following is the content of AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.mediaplayer"
   android:versionCode="1"
   android:versionName="1.0" >

   <uses-sdk
      android:minSdkVersion="8"
      android:targetSdkVersion="17" />

   <application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      <activity
         android:name="com.example.mediaplayer.MainActivity"
         android:label="@string/app_name" >
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your MediaPlayer application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Eclipse, open one of your project's activity files and click Run icon from the toolbar. Before starting your application, Eclipse will display following window to select an option where you want to run your Android application.
Select your mobile device as an option and then check your mobile device which will display your default screen:
By default you would see the pause button disabled. Now press play button and it would become disable and pause button become enable. It is shown in the picture below:
Uptill now , the music has been playing. Now press the pause button and see the pause notification. This is shown below:
Now when you press the play button again, the song will not play from the begining but from where it was paused. Now press the fast forwad or backward button to jump the song forward or backward 5 seconds. A time came when the song cannot be jump forward. At this point , the notification would appear which would be something like this:
Your music would remain playing in the background while you are doing other tasks in your mobile. In order to stop it , you have to exit this application from background activities.