How to get the name of a song from id?

Any ideas to why this doesnt work?

local id = game.Workspace.Sound.SoundId
currentsong = game:GetService("MarketplaceService"):GetProductInfo(id).Name
print(currentsong)

"unable to cast string to int64"

The problem is that Roblox can't convert your string to a number, because your sound ID is probably like "rbxassetid://"

You could use string.match() with the %d+ string pattern, get the substring, store the ID number in a script, or do something else.