Methods and apparatus teach a digital spectrum of a file. The digital spectrum is used to map a file's position in a multi-dimensional space. This position relative to another file's position reveals distances between the files. Closest files can be grouped together. When contemplating voluminous numbers of files for digital spectrums, various methods include: concatenating all such files together to get a single key useful for creating a file's spectrum; or compressing files individually and combining their collective dictionaries into a single dictionary with or without the use of tree mechanisms that defines the digital spectrum. Each provides advantage over the other. The latter consumes considerably less run time because each compression event can be distributed to a separate processor. Method two provides better spectrums because it is more “informationally” valid than is method one.