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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Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
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Batch merge and/or delete playlists
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Locates pairs of track entries pointing to the same file
downloaded 14m 49s ago
Remove iTunes tracks disassociated from files
downloaded 21m 5s ago
Re-locate files of selected tracks to new folder, preserve track meta-data
downloaded 21m 21s ago
Remove selected tracks and Trash or delete their files