Rank beginner here: When I start BiaB 2021, I get an orange popup menu saying the input and output sample rates don't match. I've followed the instructions to select the same input and output rates from the Sound Control Panel, but no matter what I do, I still get the error.

I get the same / similar yellow popup in RealBand 2021 -- Input and output devices are set to different sample rates.

Any idea how to resolve this, or is it even worth worrying about at this point?

This is referring to your Software (BIAB) and your hardware (Wins or your external sound device) transfer of data. If it is not the same you will hear some garbled or popping or screeching noises. The message is telling you to make an adjustment so they are sending and receiving at the same rate (KHz).

Their are three common options, 48kHz and 44.1kHz and 96 kHz. These settings can be easy to find or not. Depending on your system. My Motu Audio Express is smart and can self correct based on what the software is using. So I have not had this issue in a long time. I do believe for years BIAB was 44.1 but in 2020 gave us all three options.

Hope this helps. Should be a simple setting fix.

Thanks. I'm using the onboard sound card on a Dell laptop rather than a dedicated audio output device.

I've reverted to factory settings multiple times and still no joy. I've tried setting the sample rate everywhere I could think of within the program and in Windows (10) settings, and still get the error -9997 whenever I reload the program.

I'm in Driver Hell, I think.

That Dell Laptop is likely 44.1 KHz. So set BIAB to same in "Audio\Render to Audio file". If that don't work, someone else who knows more than I will come along.

The setting in Windows selects the default sample rate - applications can request a different sample rate as necessary, so it's usually not an issue.

Band-in-a-Box does have a resampler, so even though the Realtracks are all in 44.1khz it should play back properly if set to a higher sample rate. In practice, some sound drivers do not behave nicely, so a common fix for us is to set the default sample rate to 44.1khz.