A Renoise song is the save format for musical projects in the Renoise software. There are a number of different versions of it, created by different versions of the software.
In the XRNS format, the file is actually in ZIP format, containing an XML file (Song.xml) and a SampleData directory with subdirectories for each music sample included in the song, in turn containing FLAC files. An optional icon in PNG format (Icon.png) may be in the root of the ZIP.
The XML file includes embedded data as well as various elements giving parameters and organization of the data.
The top-level element is
<RenoiseSong doc_version="54"> (with varying version numbers).