Both .rcy and .rc2 files are audio loops from the ReCycle audio editing program from Propellerhead Software, maybe just from different versions of the tool. It is very likely that doing rcy to rc2 conversion with the original tool is a trivial thing, but if you do not have access to it, you will have to rely on some 3rd party apps that feature ReCycle format support. Unfortunately, there won't be that many options.
Updated: August 14, 2023