Once guitarists figured out what Eddie Van Halen was doing, tapping became another flash trick, like pinch harmonics and whammy bar wiggling, that could be used to sound cool Stevie Ray Vaughn Greatest Hitswhen you couldn't think of anything else to do.
For a while there, two-handed tapping had quite the stigma about it. Although players like Frank Zappa, Jimi Hendrix, ZZ Top's Billy Gibbons and Genesis' Steve Hackett had all experimented with prototypical forms of tapping in the '60s and '70s, Eddie Van Halen really developed the style into a phenomenon, starting with "Eruption" in 1978. And then the imitators came. Once guitarists figured out what Eddie was doing, tapping became another flash trick, like pinch harmonics and whammy bar wiggling, that could be used to sound cool.
By the time the '90s hit, tapping was virtually illegal. Overuse had sapped the technique of its originality. Now, of course, tapping is once again accepted as a valid style, and players are taking it in interesting new directions one of which has its roots in Stanley Jordan and '80s players such as T.J. Helmerich (who has a knack of continuing to get better and better, too, by the way). It has continued to grow in the hands of players like Megadeth's Chris Broderick. This style involves playing basslines or chords with one hand while executing a melody or harmony with the other, and although it can be a little daunting at first, after a little bit of work it can start to feel more natural. Although it's great as a flashy rock or metal technique, a cleaner tone is required so you can hear each note clearly. It's especially suited to blues and jazz styles and there's a world of indie experimentation out there just waiting for an enterprising guitarist to explore.
For the best results and playability, you'll need a guitar with relatively low action. Some light compression may help you even out dynamic variations while your hands get up to speed, too after all, even if you regularly employ Van Halen-style tapping, the fingers of your fretting hand may not be used to carrying an entire melody on the fretboard.
Let's look at a blues example in the G Minor Pentatonic scale. First, use your "regular" fretting hand to hammer the following pattern. Try to flatten out your fretting hand fingers against the fretboard just enough that they mute any unneeded notes, but not so hard that they sound phantom notes themselves. And note the simple G5 power chord at the end.
Next, we're going to add a simple melody in the well-known pentatonic box shape, tapping the tips of the fingers on the fretting hand. Use whichever fingers are comfortable for you it's great if you can use all four digits, but if only your index and middle fingers are strong enough for now, use those to get the melody into your head (while still practicing to build up the others). Note the slight quarter-step bend on the second last note. This will add a little bit of sass to the lick while setting up a nice resolution to that G note on the 17th fret of the D string at the very end.
Now it's time to put it all together.
Finally, we're going to add a little swing to the whole shebang. Offset each melody note with a laid-back shuffle groove (think Stevie Ray Vaughan's Pride and Joy). As you become more comfortable with the technique you'll be able to add more articulation more slides, more bends, vibrato, etc.
There are a million ways to employ this style, but I find that this kind of rhythmic/pattern-based method is the best for getting your fingers used to the whole idea. From there, you can incorporate chords, more sophisticated walking basslines and some really out-there counterpoint parts.
Thanks to Peter Hodgson, Gibson.com.