Hi ToniRichter,
Welcome to the Sony Community!
You can use the PlayMemories Home software to add music to your videos. You can also control the volume of the audio, trim and put captions on your video. Please click this link and look for the Multiple Edit tab to learn about this feature.
For further assistance, we recommend contacting the Sony Support Center in your region. Please visit our Sony Global Web site for information at http://www.sony.net/SonyInfo/Support/.
If my post answers your question, please mark it as "Accept as Solution". Thanks_Mitch