There is an affinity for slide blues inside of me that is begging to be satisfied. However, I apparently lack the skill to currently make a slide sound good. Yes, those who have the slide-skills are truly captivating at making something so technically savvy look effortlessly simple. Mostly though it is the sound and resonance of slide guitar that makes it so captivating and haunting to me. much like pickups and woods on a guitar, material has a lot to do with the tone you will get from a slide.
Since its beginning, slide guitar has seen many materials and designs used but the two that remain the most popular are slides made from Brass or Glass. First off, I have always been a proponent of the saying “more mass = more tone”. With this thought in mind lets look at the differences between glass and brass and see what we might discover about their individual tones. Like most thing I study I first look up definition and history of my topic; this proved to be very helpful. The forth definition for Brass was: “impudent aggressiveness”. Glass on the other hand said it was “transparent” and “without structure”
Just by taking into consideration those definitions alone i can pretty much assume what tones i will be getting from my brass or glass slide but lets take it a bit farther. Glass, according to the Greeks, is “amorphous” or without a crystalline structure like solids such as metals have. Another way of thinking about this is that Glass is like Water, the volume and mass are there but the ability to hold and maintain shape isn’t so prevalent. Have you ever been in a old house with single pane windows that have shrunk or sag due to the pull that gravity has on them over time? Glass isn’t going to give you the clarity in the lower frequencies that you might find from a harder material that has “structure” but there is one aspect to a glass slide that makes it unlike any other material and that is its “transparency”. Glass slides have a way of presenting the sound of the guitar without adding any of it’s own tonal character. some people say that glass' sound is smooth or rounded; i like to say it molds the sound. the highs and lows aren’t as defined so you get an overall milder or softer, blended tone.
Brass on the other hand, as stated earlier, is “impudently aggressive”. Just so we are on the same page, something impudent is something that is “improperly forward or bold”; exactly. Brass, being a true solid, has the mass and structure to boldly deliver your chords and notes. Sure you might not be fretting the strings to produce the truest tone but as "improper" as a brass slide can get, your sound and notes will be present and defined. Unlike glass, brass also is known for its sustain. Since metal is a true solid it has the rigidity to not absorb a plucked string's resonance and therefore allows the string to maintain its energy and true sustain.
Well, now that we know what slide to get, all we have to do practice for the rest of our lives. Then maybe one of these days we will all master the unique beauty of the slide guitar. Until then, keep rockin’… and rollin.