Sure, iTunes can join tracks, but only if they're consecutive CD tracks, and you haven't imported them. This script allows you to join any two (or more) MP3 tracks (repeat: MP3 tracks only), provided that they are the same format and bitrate.
Also see Join Together, an application that will join any type of files.
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Export files of tracks in two or more playlists to single folder
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Remove iTunes tracks disassociated from files
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Displays files in iTunes Media folder not in iTunes track library
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Removes leading and trailing space characters from chosen tags in selected tracks
downloaded 25m 7s ago
Exports and then re-imports selected tracks' artwork
downloaded 25m 13s ago
Copy number prefix in Song Name of selected tracks to their track number tag