Originally Posted by: mlynn1I just watched a You Tube video on modulation and was blown away. Why isn't this taught more often. It adds so much to a song with little extra effort.You just need some help with the theory behind it. I wish Guitar Tricks would teach this. Maybe they will. I hope so. Thanks! Mark

These tutorials on improvisation cover modulation.

www.guitartricks.com/tutorial.php?input=876
www.guitartricks.com/tutorial.php?input=491

This tutorial on music theory covers secondary dominants, which are the main music device used to modulate.

www.guitartricks.com/tutorial.php?input=495

This tutorial on the circle of fifths also covers secondary dominants & modulation in a few different genres.

www.guitartricks.com/tutorial.php?input=835

Hope this helps. Ask more if necessary! Have fun. :)