MP3+G is the brainchild of the TriceraSoft software company. It has become the industry standard computer karaoke song file format. Basically it can be defined as the compressed version of a CD+G disc song track. Each MP3+G™ song consists of two files which are one mp3 audio file and one cdg file that contains the lyrics and images. Like CD+G song tracks, MP3+G™ songs are not videos even though they both contain scrolling and highlighting lyrics.
One important fact about MP3+G™ files to keep in mind is that the two files must be named exactly the same, including spaces, with the exception of their file extension. They are also case sensitive. Both files must reside in the same directory (folder).
To make the file pairs easy to manage they are very often zipped together into a single zip file. If you have come across the term "karaoke zips" this is what it is referring to. Virtually all modern karaoke software supports zipped MP3+G™ files. Sites that sell MP3+G™ files as downloads offer them as zip files.
MP3+G™ files are excellent for backing up your CD+G disc collection to a hard drive as they are drive space efficient and can be returned to the CD+G disc format with the proper software. They are also the most commonly used file type used by karaoke hosts who run their shows from a laptop with hosting software.
There are several ways of obtaining MP3+G™ song files. With software like Power CD+G Burner you can rip the song tracks from CD+G discs directly to zipped MP3+G™. You will find details on this in the Transfer CDG Song Tracks to a Hard Drive tutorial. There are sites like TriceraSoft that sell downloads. Most karaoke CD+G disc manufacturers now offer their songs as MP3+G™ as well. There are karaoke streaming services, like the Karaoke Cloud for example, that offer monthly fee subscriptions to their song libraries.
Finding free MP3+G downloads can be difficult to say the least. Web sites that post commercial karaoke songs for free will usually be quickly shut down. P2P applications will find some karaoke songs but these are notorious for spreading computer viruses. You may find some karaoke torrents but the selection is very limited. Your best bet by far is the karaoke file sharing channels like those found with the MP3+G Download Guide.
It is not possible, or at best extremely difficult, to edit the cdg portion of an MP3+G. With the proper software you can change the key and/or tempo of the mp3 audio without affecting the synchronization. Programs like Microstudio and Power CD+G Burner make it very easy to create CD+G discs from MP3+G files.