An ‘instrumental’ is a version of a jingle without any sung vocals being present. It is very similar to a music bed and often they refer to the same thing. However, an instrumental is more commonly associated with the entire length of a jingle whereas a music bed is more commonly associated with a specific section of a jingle.
Instrumentals have the benefit of allowing for a voice over to be spoken over the top while still maintaining the sound of the jingle. They can also be used very effectively for subtlety. Once listeners are familiar with your jingle, you may choose to use the instrumental jingle in places where you don’t want the jingle to be the focus, but you still want to maintain the vibe of the jingle the message that it sends.
For more definitions, read the post jingle lingo, what does it all mean.