A slide is a guitar articulation technique in which you play a note and then move your left-hand finger along the string to a different fret. This technique enables you to connect two or more notes smoothly and quickly. It also enables you to change positions on the fretboard seamlessly.
The name of this technique, slide, gives you a pretty good clue about how to play it. You slide a left-hand finger up or down a string, maintaining contact with it, to arrive at a new note. Sometimes, you connect two notes (for example, you slide from the seventh fret to the ninth), and sometimes you connect a note (at a given fret) with an indefinite pitch (you produce indefinite pitches by picking a string while you gradually add or release finger pressure as you’re sliding).
Many different types of slides are possible:
Slides connecting two notes with a slur: The following figure shows a slur (curved line) along with the slanted line, which indicates that this is a legato slide. This means that you don’t pick the second note. Play the first note at the ninth fret normally, holding the note for one beat. At beat 2, while the string is still ringing, quickly slide your left-hand finger to the twelfth fret, keeping full finger pressure the whole time. This action causes the note at the twelfth fret to sound without you picking it.
Slides connecting two picked notes: The following figure notates a slide without a slur; you do pick the second note. Play and hold the ninth-fret note for a beat; then, at beat two, slide up to the twelfth fret — maintaining full finger pressure as you go — and strike the string with the pick just as you arrive at the twelfth fret.
If you play the slide in this figure slowly enough, you produce what’s known as a glissando. A glissando is an effect that you hear on harps, pianos, and guitars, wherein all the notes between the two principal notes sound.
Ascending immediate slide: An “ascending immediate slide” is a quick slide, not in rhythm, that serves to decorate only one note. It isn’t something that you use to connect two different notes. In the example shown in following figure, you slide into the ninth fret from a few frets below.
Start the slide from about three frets below the target fret (the sixth fret if the ninth fret is your target), using minimal finger pressure. As your finger slides up, gradually increase your finger pressure so that, as you arrive at the target fret, you exert full pressure. Strike the string with the pick while your left-hand finger is in motion, somewhere between the starting and target frets (the sixth and ninth frets, in this example).
Descending immediate slide: A “descending immediate slide” usually occurs after you hold a note for a while. It gives a long note a fancy ending.
Pick the note that the tab indicates (the one on the twelfth fret in this case) in the normal manner. After letting the note ring for the indicated duration, slide your left-hand finger down the string, gradually releasing finger pressure as you go, to cause a fading-away effect. After a few frets, lift your finger completely off the string.
Long slide: A long slide is simply a descending immediate slide that goes nearly all the way down the neck, releasing finger pressure (and finally removing your finger from the string) toward the end of the neck, as near to the nut as you want to go.