What you are looking for is sound service

Here is an example on how to add more bass to a sound:

For starters, we have Sound1 in workspace.Part

1) Scroll down in the explorer in studio, and right click on SoundService, then hover over insert, and insert a SoundGroup

2) Insert an equalizer into the SoundGroup

3) Click on the equalizer object, then in properties you should see:

• High gain
• Low gain
• Mid gain

4) Low gain is the important one, move the slider past 0, adjust it to how much you want, I found that anywhere between 3 - 10 decibels is effective, but it depends on the song and your opinion. For example, move the slider to or enter in the number 5.

5) Go back to workspace in the explorer, click the sound, then look at the SoundGroup property. Click the Empty space and scroll down to SoundService, then click on the SoundGroup you just created.

I hope this helps!