John Mayer and Taylor Swift have been known to show up at each other's concerts, play some songs together and have a ongoing Twitter love fest (no, no, not dating). The pop songwriter has long threatened to have her appear on his album, and now he's making good on it with "Half of My Heart."

The track will appear on "Battle Studies," due Nov. 17, which also features "Who Says," as reviewed here.

The track may be called "Half of My Heart," and it is technically a duet, but don't expect the country superstar to be an half of the song. Just listen closely in the chorus and the back-and-forth on the bridge... aaaand that's it. Very little personality from the country queen, but keep in mind that this is clearly Mayer's show.

Otherwise, the song is a harmless, mid-tempo acoustic rocker, with a guitar line that immediately evokes Tom Petty and Dire Straits and the melody line of latter day Ryan Adams.

In more Mayer news, the singer-songwriter has set a full tour in support of "Battle Studies," starting in February. Tickets go up for general onsale on Nov. 21. Michael Franti & Spearhead have been tapped to open. Now, let it absolutely be said that Franti is a genius, a longtime musical veteran of infinite worth -- but is also an excellent pick, as he is definitely not a person to tell Mayer he "can't get stoned."

Here are John Mayer's tour dates:

February
8          Mon                    Charleston, SC                        North Charleston Coliseum
9          Tue                     Birmingham, AL                     BJCC Arena
10        Wed                   Nashville, TN                          Sommet Center
12        Fri                       Auburn Hills (Detroit), MI     The Palace of Auburn Hills
13        Sat                      Toronto, ON                           Air Canada Centre
16        Tue                     Ottawa, ON                            Scotiabank Place
17        Wed                   Montreal, QC                          Bell Centre
19        Fri                       Uncasville, CT                        Mohegan Sun
20        Sat                      Washington, DC                     Verizon Center
21        Sun                     Philadelphia, PA                     Wachovia Center
24        Wed                   Boston, MA                              TD Banknorth Garden
25        Thu                     New York, NY                       Madison Square Garden
28        Sun                     Grand Rapids, MI                   Van Andel Arena

March
1          Mon                    Milwaukee, WI                       Bradley Center
2          Tue                     St. Paul, MN                           Xcel Energy Center
4          Thu                     Omaha, NE                             Qwest Center
5          Fri                       Oklahoma City, OK                Ford Center
6          Sat                      Houston, TX                           Toyota Center
8          Mon                    Austin, TX                              Frank Erwin Center
9          Tue                     Dallas, TX                               American Airlines Center
10        Wed                   New Orleans, LA                    New Orleans Arena
12        Fri                       Columbus, OH                        Nationwide Arena
13        Sat                      Louisville, KY                        Freedom Hall
15        Mon                    Greensboro, NC                      Greensboro Coliseum Complex
16        Tue                     Charlottesville, VA                 John Paul Jones Arena
17        Wed                   Atlanta, GA                            Philips Arena
19        Fri                       Memphis, TN                          Fed Ex Forum
20        Sat                      St Louis, MO                          Scottrade Center
22        Mon                    Kansas City, MO                    Sprint Center
23        Tue                     Denver, CO                             Pepsi Center
25        Thu                     Los Angeles, CA                    Staples Center
26        Fri                       San Jose, CA                           HP Pavilion
30        Tue                     Portland, OR                           Rose Garden
31        Wed                   Seattle, WA                            KeyArena

April
1          Thu                     Vancouver, BC                       General Motors Place
3          Sat                      Calgary, AB                            Pengrowth Saddledome
4          Sun                     Edmonton, AB                       Rexall Place
6          Tue                     Saskatoon, SK                        Credit Union Centre
7          Wed                   Winnipeg,  MB                       MTS Centre
8          Thu                     Fargo, ND                               FargoDome
10        Sat                      Chicago, IL                             United Center