Your CD player should have a "repeat" function. You just turn "repeat" on, and it will play the CD over and over and over automatically.
You could also create an .mp3 file to play on an MP3 player, most of which also have a "repeat" function.
I use 2 small MP3 players run to battery powered speakers or computer speakers. Crows calling looped on one, my witch cackling and spellcasting mixed with her bubbling cauldron on the other. Since the players are so small they are easy to hide on or in a prop.