Does digital audio related questions belong here? If I'd ask a question that has nothing to do with video but focusing on audio only (mainly software-side), would be that marked as 'off-topic'?
Should these kind of questions go to Superuser?
No and No. Sound related to video is on topic here. Sound that is purely sound related would go on Sound Design as long as it is production rather than consumption oriented.
Audio for specifically for music production is also usually on-topic at Music Practice & Theory.