Keyframing audio/transitional bass

What I want to do is very simple: I want a transitional bass sound where it goes from full to none, like you’d do with keyframes in any video editing software.
Is this possible?

As in, the bass fades out?

There are many ways to do this, but there is no keyframe-style method. If you learn how to crossfade and how to use a highpass, you will be able to do it.

If you are making a mix, I would not recommend using Audacity.

Any particular type of bass sound? Are you wanting to generate a bass sound, or is the bass sound already in your recording?