NeoHomeBrew (./116) :
Hi, sorry for the late response (i was on holiday). Thanks for your comments
Because I am working with the NeoBitz NeoSoundbuilder I can only play ADPCM-A samples and as far as I know these are limited to max. 1 MB on the NeoGeo CD-Systems.
I need to find a way to play CDDA audio files for the background music on CD-Systems (https://wiki.neogeodev.org/index.php?title=CDDA)... did someone eventually tried it already?

Didn't the Tetris homebrew game (download in link below) use CDDA? I haven't burned it yet, but the download contains the iso and 2 audio files, maybe open the iso and see what you can find in the code?

http://neogeocdworld.info/medias/iso/

If you need someone to test on real hardware I'm willing to burn a few coasters for the cause!