Renoise .xrns files aren't similar to .mod at the byte level at all. .mod is raw binary: fixed header (song title, 31 samples, order list), then packed patterns (4 bytes per note: period/inst/vol/effect) and 8-bit PCM sample data. No container, minimal compression. .xrns is a ZIP archive (rename to .zip to open) with XML for all song data (patterns, sequences, effects, automation) plus embedded samples as FLAC (lossless compressed) or WAV. Renoise imports .mod fine for old projects, but the formats are night-and-day different structurally—classic tracker purity vs modern XML flexibility. Same for .it vs .mod: .it is a direct evolution (more channels/effects, optional sample compression) but still binary.