Automating import of songs from a list into iTunes?

I would do this in bash rather than Applescript so I hope you just want a result rather than worrying about the method. You can run the commands below by typing them into Terminal.

So, first thing is to generate a list of all your tracks and save it in your HOME folder as TRACKS. I can't see what your disk is called or how things look on your machine but you want something very similar to:

find "/Volumes/DRIVENAME/General Music" -type f > $HOME/TRACKS

You should be able to check if it is correct with:

cat $HOME/TRACKS

Now you want a script to search for items from SL in there. So you need to save the following as $HOME/searcher.sh:

#!/bin/bash
while IFS=$'\t' read title artist year ; do
   echo Searching for title: $title, artist: $artist, year: $year
   grep -i "$title" TRACKS | grep -i "$artist" | grep "$year"
done < $HOME/SL

That assumes your SL file is in your HOME directory.

If you use TextEdit to write the script, ensure it is plain text, see here.

Now you need to make that file executable (necessary just once) with:

chmod +x $HOME/searcher.sh

Then you can run it with:

$HOME/searcher.sh

and see if it identifies the tracks. If that works, we can get those tracks into Music as a second step.

Second step... don't start on this till first step is looking good. Also, reduce your SL file to just 2-3 lines in case it goes wrong so there's not too much to put right!

So, if the above finds your files, we now need to add them to a playlist. So, manually make a playlist yourself, say "Old Stuff", then change the code above so it looks like this:

#!/bin/bash
while IFS=$'\t' read title artist year ; do
   echo Searching for title: $title, artist: $artist, year: $year
   this="$(grep -i "$title" TRACKS | grep -i "$artist" | grep "$year" | head -1)"
   osascript -e "tell application \"Music\" to add (\"$this\" as string) to playlist \"Old Stuff\""
done < $HOME/SL