The .cue says if it is or not. 😁
Buuut... sadly.....
Redbook with vsbhda may be a crapshoot.
there are numerous reasons for that, but mainly, dos CDA is an analog thing, first and formost. It comes straight out of the cdrom drive and gets mixed by the soundcard through a designated input. If you are using vsbhda with an awe 64 gold or something that HAS CDA inputs, then there's a good shot at it working.
If you are using vsbhda with an HDA device that lacks such an input... ... well...
To be more clear:
A cdrom drive can be instructed to play an audio cd track by a program with very simple commands. THIS is what most DOS games the use CDA do. They just tell the drive to play a track, starting at a specific timestamp. The drive itself then just plays out the audio on its cd audio cable, the soundcard takes that audio, and mixes it in.
From the game's pov, there is no more supporting code than that.
In *RECENT* years, the way these discs get played in a drive is quite different. The digital track is actively read by the computer, and the raw pcm data in the track is *digitally* mixed.
HDA is a modern, digital, design.
To have proper cd audio from mixed mode discs in dos, your drive, and your sound hardware, have to support analog cd audio playback.