Really a broad and deep subject for such a basic item of use for guitar players. Or uke players for that matter. Hey, just saw a YouTube clip of a bass player using a slide on part of a song as well!
So a “slide” is some sort of thing you clasp with your fingers or actually wear on a finger of whichever hand (right or left-handed doesn’t matter) you are placing it against the string/s with. You then use your other hand to pluck the strings while the slide produces notes and chords or simulated chords out of two or more strings at a time.
I use them on 1, 2, and 3 string cigarbox guitars as well as typical 6 string guitars set up exclusively for slide playing as well as a 6 string lapsteel.
Pictured are 14 (not all!) of the slides and stuff I have and actually use for slides both in recording and shows for many years. Whether copper, steel, composite metal of some sort, bone, glass, acrylic, bit of pvc, a butter knife handle, jackknife or you-name-it, they all work. Or can work depending on your willingness to figure out what best suits your aesthetic, your sense of tone, feel, your hand/finger and such.
Some like to play upright in typical playing fashion by placing a slide on their ring finger, some on their little “pinky”. The second technique works well if you set your strings high enough (“action”) on a six string guitar which means you can swap off playing with pointer, middle and ring fingers normally in pressing the strings down between the frets, then very quickly in the same song change over to slide. Often one uses normal tuning and plays on the D, G and B strings while muting the others, this gives you a basic G root chord for playing in the key of G.
A very small number of folks play “over the top” which is how I learned as a young lad. Being right-handed I placed a glass or metal slide on the pointer finger of my left hand. Australian Dave Hole plays killer slide just that way.
Lastly, there are more than a few slides lapsteel or pedal steel guitarists use, typically some type of “tone bar slide” as the nomenclature goes. They may be mostly flat and smoothly rounded on the end (I have a vintage one gifted me by a friend) or larger and heavier with easy-to-grip top indents and a larger rounded bottom for placing on the strings.
Regardless, one must have high enough string action and typically the heavier gauge strings the better for the weight of heavier slides but mainly for tone and durability (at least sometimes, thicker strings last longer).
Using a git with a pickup and setting it up for slide playing means adjusting the pickup higher to get closer to the strings but not so close as to press the strings right onto the pickup when playing. Action of strings is of course raised by adjusting the bridge and sometimes nut on the guitar (the things the strings lay across toward the bottom of the body and near the top of the neck, respectively).
You can web search for 6 and even 3 or 1 string tuning ideas and more, but on 6 stringers I normally tune to an open E chord, sometimes open D or G. As in all slide playing unless on a normally tuned 6 string git you must learn the new scales, that is, if soloing, where to find the patterns for individual notes or phrases when using any alternate (not typical E A D G B E) tuning. Practice and memory then brings good results!
As I’m a creative person and like change-ups, sometimes I might lay a guitar across my lap or play it on a keyboard stand in front of me ala lapsteel while other times I play it in normal position while seated or standing. Whatever seems most natural and comfortable to YOU is how to play slide guitar.
There are as many opinions as to what material is best re. actual tone and comfort as there are slides, that’s for sure.
My bud Shane Speal has a site you might like on this subject as well- http://www.stubbyslide.com and what he does with a portion of the loot is truly cool.
Up in http://www.cigarboxnation.com you can find a ton of info., styles of slides and playing ideas as well as instruments to play ’em on. https://www.cbgitty.com/ and also Randy Bretz (https://sites.google.com/site/diamondbackcigarboxguitars/randy-s-bone-store) does amazing work re. slides and all things related) -these are all great sites to learn and possibly pick out something you might enjoy.
Finally, tone- and this is simply saying what I hear from basic slide material: metal slides sound brighter and sometimes a bit thinner while glass puts off a “gliss” sound, smoother but with overtones and harmonics galore, composite slides vary in all these features tonally while wood (yep, they’re out there) and sometimes pvc or bone give off a warmer sound.
Hopefully this helps you consider a world of no-pain-no-callouses- guitar playing 🙂 with the sweetest and most easy way to create sweet vibrato with a guitar that I know of. Been saying this for years and I believe it to be true.
As always, thanks for stopping by! -Glenn