Shanty is a an app that allows you to record yourself singing a shanty, and then a second tool to “compose” yourself and as many others as you like. The idea is that you sing a shanty and then use the same shanty sung by others to create a full blown track. Any ad revenue is shared out to the original content posters.
This is inspired by a particulary good youtube mixup of a sea shanty. I may have reinvented TikTok, I dunno, I’ve never used it.
Not tiktok, but smule.com is pretty much what you describe.