This program is designed for specifically editing "Guitar Hero 3 for PC"'s songlist so you can make custom songs, I'll provide a brief explanation, and provide a video, not of me, for specific instructions.

1) Since I already assembled the program for you, extract the .rar to a folder, go into the extracted folder, and run "songlist_editor.exe" application.

2) You should see a brief glimpse of the command prompt, don't mind that, then the prompt should come back along with a new window that has a few boxes.

3) Assuming you already have GH3 and have installed it, go into the "DATA" folder using the file then open options in the left hand corner. The DATA file should be under the Aspyr folder.

4) After you have what looks like a slew of songs, you must find your .mid file and your .mp3 file.

*The .mp3 file is any song of your choice, granted that the website below has the chart or .mid file you need for the song. By the way if your lost by now, either give up, or just watch the video below, bear in mind the guy making it isn't the best for the job*

5) With your files, you go to "Insert A New Song" and fill the fields in with as much information as you can, uploading the files to the fields as needed, and provide as much information you can on the song, as it will appear when you play the song in-game.

6) When you tell it to start, the command prompt should start going massively crazy with random computery jibberish, I don't know what it mean but in the end you get a song, and it takes a while depending on your song.

7) Once the command prompt is done with its work, be sure to Save it all, or you wont be able to play the song.

8) Enjoy your new song, provided you did everything right, I know my explanation was sorta half ass, but that's what the video below and comments on the torrent are for.

Video Instructions:

For The Chart To .mid file Converter
Either download via the link on the video, or view my other torrents and find "Chart2Mid" 

Good luck, and have fun!

*Last note, Operation Ground and Pound by Dragonforce is awesome to make as a custom song, along with any Van Halen or Eric Clapton song, just go all out crazy!*