Yes. If you install the SBPro disks, it will register also an SBP-MIX.EXE entry in AUTOEXEC.BAT to init the mixer to good values. You can also add it yourself. To figure out the switches I think you can run SBP-MIX /?
It will list all options and switches, including the "silent mode" switch (IIRC it was /S) which will set mixer values on the command line without the UI. Just gather all the settings and build the line to put it in your AUTOEXEC.BAT.

As the above post stated, a mixer executable should be registered in AUTOEXEC.BAT after installing the software that came with SBPro2 floppy disks. In my case it was SBP-SET.EXE and that one was entirely done with command line switches.

An example:

1C:\SBPRO\SBP-SET.EXE /M:10 /VOC:15 /FM:15 /CD:0 /X:0 /LINE:0 /ANFI:OFF /DNFI:ON /Q

Should be put after setting the BLASTER and SOUND environment variables. The /Q command line switch is for silent or quiet mode.

That did it, thanks both. Not sure how I installed the software but skipped this step.
I re-ran the installation.
It's all working great now!