Using version control for module files often points out that diffing modules even on rough scale could be useful. Without being of aware of existing solutions, I wrote a little hack to OpenMPT with which it is possible to set e.g. TortoiseSVN to use mptrack.exe with appropriate command line arguments to do module diffs . Attached is the code and an example what the module diff looks like. Comparison is based on as-simple-as-possible module-to-text conversion (currently highly lossy, but covers big parts such as pattern data) and use of existing diff programs for the actual comparison. Note that this is a demonstration-of-concept type of patch and is by no means intended to be merged as such, but can be improved if this type of functionality is of interest.
 Diffing works from TortoiseSVN context menu by adding the following as handler of it/mptm etc. extensions:
"C:\Program Files (x86)\OpenMPT\mptrackWithDiffFunctionality.exe" /diff "C:\Program Files\TortoiseSVN\bin\TortoiseMerge.exe" %base %mine