In JJ1, the main melody for the music tracks is absent. Here's video showing it.

https://youtu.be/sOWdmnk1Cjw

Is this happening for everybody else, too? I loaded it up excited but was bummed out when the main tune didn't play in the menu or in the game levels.

No, on my JJ1 the Music plays as it should. I have never had trouble with the sound or music.

I don't have this problem, either, the music plays just fine for me.
Have you tried reinstalling it?

Can you post a video of it playing properly for you? I've tried changing the settings and tried out every soundcard option. There are a couple that play the melodies, but those settings cause the sound to be extremely distorted. The sound settings which aren't distorted don't play the melodies.

I don't think I've tried reinstalling it.

Can you post a video of the music playing properly for you?

Well, I am not a Video and u-tube guy. So no, I do not know how to make a suitable Video.

But it might help if you tell us which Hardware you use, the Settings of the Hardware and your Dosbox-Config Settings for Jazz Jackrabbit.

For Example: I use a Creative X-Fi Titanium HD on a Intel Z390 Board on Win10. It is configured at 24 Bit 48 kHz. So i configured Jazz 1 as following to minimize emulations/transformations:

[mixer]
nosound=false
rate=48000
blocksize=1024
prebuffer=25


[sblaster]
sbtype=sb16
sbbase=220
irq=7
dma=1
hdma=5
sbmixer=true
oplmode=auto
oplemu=default
oplrate=48000

Probably your sound settings are wrong.

Don't change any DOSBox settings (and if you have, see if you can revert them to default), but open the game, and when prompted, select "3) Sound and Language Settings"; choose your language, then go Select Sound Card, pick Sound Blaster 16, select Ultra high quality, and it should instantly be ready to go.

For those who run in the same issue, I do have a solution. Jazz Jazkrabbit works better with the Gravis Ultrasound. So what you need to do is the following:

1. In the dosbox configuration file (dosbox_jazz.conf) change the property "gus" to true to enable Gravis Ultrasound emulation.

gus=true

2. In the the sound settings set the sound driver to Gravis Ultrasound.

This solved the issue for me.