This article will show you how to add multiple ringtones to your PowerPoint presentation.
Steps

Step 1. Take PowerPoint 2007 for example
PowerPoint 2003 is like it.

Step 2. Insert a sound file (suppose our presentation has 20 slides and we want the melody to sound from 5 to 8)

Step 3. In slide 5, click insert -> sound -> sound from file
Select the music you want to insert.

Step 4. In the next dialog that says
"How do you want the sound to start in the slideshow" select "Automatic".

Step 5. In the ribbon, click Animation -> Customize Animation

Step 6. In the Animation Settings task pane, click the arrow on the selected item in the Animation Settings list and select Effect Settings

Step 7: On the Effect tab, under Stop Playing, click After * Slides, and then enter 8

Step 8. On the Time tab, under Repeat, select End Slide

Step 9. After that, the melody will play from 5 to 8 slides
If you want to add another sound file to the same presentation, do the same.