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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downloaded 5m 2s ago
Sort purchased tracks into discrete playlists by name or Apple ID
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Change file type to make selected AACs bookmarkable
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Perform search-and-replace on text in your choice of tags
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Set choice of various number tags of selected tracks incrementally
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Append user-entered text to beginning or ending of selected tag of each selected track
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Applet assists with swapping, copying, appending data between track tags