Wow, you know your music business! Actually though, touring and ancillary merchandise sales are a large percentage of a musicians income as well.
As for the various types of royalties you mentioned, the performance one is for the actual performance on the recording. This one pays on a per unit (disc, tape, etc) basis. The typical major label rate is $.08 to $.11 per disc. Rather pathetic, to be honest. Business models like Ani DiFranco's Righteous Babe records, a self owned label, have proven far more profitable.
The mechanical is paid based on airplay. Soundscan, an independent monitoring company, keeps track of how many times a given recording is played on radio, and broadcasters pay a fee per playout. MTV, however, has managed to skirt around paying mechanicals since they term music videos as promotional material, and not a musical performance. I've yet to see anyone take on MTV to payout mechanicals, and they probably won't for fear of being blackballed by one of the biggest forces in the music industry. Ironic, since MTV made their name playing music videos, but barely shows them at all anymore.
Print income is for sheet music sales. This is usually a partnership with a publishing house that will do the actually score printing, and take a percentage of the sales as a fee. This is a very low percentage source of income.
Synchronization fees refer to film or television use of a song in a given production. Fees must be paid for rights to use the song. In the case of every artist, it's imperative to hold onto these publishing rights, as syncing fees can bring in serious money. A single track being put on a movie soundtrack and placement in a major motion picture can easily run a couple hundred thousand dollars for a low level band on a major label. A band I know was set to appear on the "American Wedding" soundtrack, and they had negotiated a fee in the mid 100 thousand range. Too bad the deal fell through for them.
Additionally, merch and touring are big income draws. Far bigger than most people realize. It dwarfs the $.08 to $.11 per disc that most major label artists earn in their performance royalty. Bands like Metallica (an extreme example) have made themselves rich for a lifetime because of touring and merch.