The discussion continues on this thread: Re: SBPro1 CT1330A owners, care to help figuring things out?
It is already confirmed that the SBPro2 CT1600 DSP v3.01 and v3.02 will always start a fresh PCM stream from the first left sample, no matter on what sample the last stream ended.
In other words, SBTEST will always play the Left channel in both tests on all revisions of the SBPro2 CT1600 cards.

EDIT:
It is confirmed that CT1330 Rev.05 and 06 behave exactly the same as CT1600, they play twice on the left channel.

EDIT:
CT1330A Rev.04 also behave exactly like CT1600.
Re: SBPro1 CT1330A owners, care to help figuring things out?
DOSBox has the SBPro emulation reversed and the extra byte has not effect whatsoever on the real SBPro cards, only on the clones.

ripsaw8080 wrote:

A direct modification of the Miles SB16 driver has some advantages over the swapstereo patch: […]
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A direct modification of the Miles SB16 driver has some advantages over the swapstereo patch:

1) It doesn't require an unofficial build of DOSBox; and if you're using an unofficial build that doesn't have the swapstereo patch, it will work there as well.

2) It targets only the SB audio. The swapstereo patch reverses the channels of all inputs to the mixer.

3) It has an effect at the point where it's needed. The swapstereo patch is unaware of when the channels first become reversed, which can be a problem when the channels are reversed in-game, but not in videos.

A brief explanation of the issue with the driver: it sets up two samples worth of data for its initial stereo DMA transfer, but for some reason instructs the DSP to use only one sample, resulting in reversed channels because DOSBox keeps track of "leftover" samples from previous transfers. The issue with DOSBox is avoided by changing the driver to use both samples; and the modified driver still works correctly on a real SB16.

To modify the driver, run the attached program inside DOSBox in a folder where SB16.DIG is located (preferably an installed copy). The driver file has several variations, so the program searches for the correct offset to modify. If you encounter a version of SB16.DIG that the program does not recognize, and you're sure it is a Miles AIL3 driver, send me a PM so I can examine it.

The swapfix.exe patch doesn't work here: it does patch the SB16.DIG of Albion and Magic Carpet 2, but audio is still reversed here with DOSBox 0.74-3 stock.
My .conf: https://hastebin.com/afoqohinan.makefile

My PC specs:
Gaming Laptop ASUS GL703GS (BIOS 310)
CPU i7-8750H (iGPU unavailable)
GTX 1070 8GB (non-Max-Q, vbios 86.04.7c.00.24, Samsung VRAM)
Windows 10 Pro 1903
Desktop res: 1080p (1920x1080)
Screen: 144Hz + g-sync AUO B173HAN03.2 [AUO329D]
Audio: Realtek HD Audio (ALC295 chipset)
Hard disks: NVMe Samsung, SSD Crucial
USB Blu-Ray 4K drive: Archgon Star MD-8102P-U3YC-UHDB (Pioneer BDR-UD04)

EDIT:
Solved! Didn't change in my .conf file the sbtype=sb16 (since SB16.DIG was patched), ooops!
Thanks ripsaw8080

HunterZ
BTW, it is Munt resp. the MT-32 which has swapped stereo output, this is very obvious if you keep in mind that the MT is intentionally a standalone synthesizer and stereo has to be swapped for you as player to be correct for the audience, at least this is what i assume as reason for the swapped channels of the MT.
If we take the piano as reference the listener will hear the lower keys on the right side while for the piano player they are left on the keyboard.
This will be the initial setup for the MT-32.

FYI, Terra Nova is still reversed with DOSBox 0.74-3 (and both DOSBox ECE and the 0.74-3 derived build bundled with the GOG release). Tested both the GOG version and installed from ISO + patched to official 1.09.

ripsaw8080's SB16.DIG patcher fixes it, and is therefore a good option because it works even with DOSBox versions lacking a swap config option:
Re: Invert Left/Right Audio Channels Stereo Sound?

Edit: Here is a patched SB16.DIG from Terra Nova for people's convenience.

Edit 2: Battlespire has the same problem. The Terra Nova file seems to work, but is different from Battlespire's, so I've added the patched Battlespire file just in case it matters.