Purchase a greeting card sound module from an online gift supply retailer, such as Sound Expression, AGC Sound or Woomaa. The amount of time you will be able to record audio onto your module depends on the model you own. Times range anywhere from 10 to 30 seconds.
Remove any protective tabs that prevent the battery from making contact. This protective tab or tape is underneath a metal latch on some models.
Press the red button and record your greeting. This greeting can be either your own voice or a song from a phone or radio that the person receiving the card would admire.
Pull the bendable tab to test your recorded greeting. The bendable tab will trigger the audio recording when someone opens it at the hinge of the card.
Make the card. Measure and trace a 4.25 X 5.5 inch square of construction paper with your ruler, then cut it out with your scissors. Fold the card to its side, matching up each of its four corners properly.
Decorate your card to taste with colored pencils and pens. Leave space for the sound module within the card. Be careful that that words and images do not make their way into the space reserved for the module, or they could be covered up from the reader.
Glue the back of the sound module to the card, aligning the bendable arm of the module to the crease in the card. Once the glue dries, the card will trigger the audio recording when opened.