SLIDE GUITAR TUNINGS ANALYSIS:
Like most other Music subjects, the evolution of Guitar tunings could take many books to cover completely; So for this webpage I can only hit the highlights and more important aspects of the hows and whys of Guitar open tunings. Remember that the main framework of tunings and methods of playing slide guitar we have inherited, and upon which most Slide Guitar is based, came long before custom string gauges, Pedal Steel Guitars and Whoopie Cushions! So for the purposes of this article, pretend we are back in the times when Black Diamond guy-wires were mostly all we could buy to string our Guitars with; That will help our brains not be so quick to interject "BUT ... BUT ... BUT", and better understand how and why we got the tunings that were handed down to us.
Open and custom tunings have been with the Guitar since it's beginning, having evolved with string instruments and the searches for the best way to tune them. Open tunings of chord voicings were certainly rather common when Slide Guitar came upon the scene in the late 1800s. Slide Guitar and open tunings lent well to each others' characteristics.
Because the Guitar had an academic tuning we know as the standard Guitar tuning, that tuning dictated what voicings (note arrangements) would occur with each open chord played, which are the chords played close to the nut and have 1 or more unfretted strings (open strings) as part of the chord notes. It stands to reason that open tunings would evolve that were similar to the familiar voicings of the chords played by finger fretting the open chords of the standard Guitar tuning. Chord voicings of both the open and standard tunings are based upon the triad notes (notes 1, 3 and 5) of any particular Major scale, arranged in various different note combinations. One simple FULL chord of 3 notes might be 1, 3, 5 while another is 3, 5, 1 and yet another might be 5, 1, 3. With 6 strings on a Guitar, the voicing for the common open C chord is 3, 1, 3, 5, 1, 3. (see the C chord illustration on the left). But tuning a standard set of Guitar strings to just any note you might desire cannot be done because of the physics involved in standard Guitar strings; Which is why they are all different sizes to accomondate a different and small range of notes for each string's different tuning tension.
Each Guitar string is manufactured to be tuned to a rather small range of notes, because each and every note has a proportional string mass, length and tension (and other physical considerations) that creates that note the best. String mass is made at the factory and cannot be changed. String length is determined by the Guitar's size ... more specifically, the length between any Guitar's nut and bridge saddle (and some extra to attach the strings) and therefore cannot be changed. So that leaves us with string tension as the main parameter we can change on that string; But since the string tension must be in a range to match the strings mass and length, we cannot make that tension too loose or too tight or the notes it was designed for will suffer exponentially the farther a string is from it's intended tension.
Up until the mid 1960's, string manufacturers decided the abstract of what the mass and length of each string in a string set should be for the different standard Guitar sizes (bass, baritone, spanish, tenor, ukulele, etc). You got what THEY determined was correct for the kind of Guitar you had; Custom string gauges were extremely rare. Informed and demanding Guitarists would take different string gauges made for other string instruments and make up their own string sets. So prior to that time, the standard set of Guitar strings would only allow each string to be tuned to a rather narrow range of notes ...about 3 half steps lower and 3 half steps higher than what the string was designed for. Therefore no matter what chord you wanted to open tune a Guitar to to play slide, the 6th string for example was rather restricted to notes between Db and G.
SO WHAT DOES IT ALL MEAN MR. NATURAL? "Well Chilluns, ....twas ever thus:" Since each string has a rather narrow range of notes to be tuned to, we can see that the 6th string for instance, being made to tune to the note E, lends itself to be tuned in a range from about Db to G. So no matter what chord I want to open tune my Stella to, the 6th string must be tuned between those notes. Well don't shoot the milk cow Gertrude ....that's pretty easy to figure out by just tuning to the finger-fretted, standard Guitar tuning, open chords, ...since they already show the note voicings for each chord that will work for each string ...and the string tensions won't be any lower or higher than 3 half steps. Lordy-be Pa, ...I already had the shotgun loaded.
So now we see how folks long ago worked around the physics and easily found the voicing limits for each chord's open tuning. It don't take rocket science to figure out that different open chords were favored by different people for many different reasons; ....such as the key they or their sidekick sang or picked in the most. That's what we inherited and we work around that common sense because others already figured out the "best" ways and set those sounds we are atuned to and build upon, ...and it works pretty darn good.
Each open chord tuning / voicing has distinct sounds, mostly to Musicians, but also recognized by more than a few in the audience. For instance, at first glance we would assume that open C and open D would sound almost the same since their root notes are only a whole step apart. But their voicings make them sound very different from each other, particularly in open tuning ...and especially if the D is dropped-D tuning (the 6th / E string dropped down to D/1 rather than up to F/3 for an open D chord). Drop D tuning's open chord sounds like it is almost an octave lower than C tuning's open chord. D tuning, especially drop-D, has a much deeper, more mysterious sound than C, ...while C sounds quite folky in it's tone-center pitch and voicing. When you hear Folk Blues played in C with either open / fretted chords or with open tuned slide, it has a distinct folk sound. On the other hand, dropped D seems to have swamp frogs singing half-time on the downbeat in the background. FRAWGS PA? ...WHAR'S MAH 3-PRONG? "Well you finish up lappin the valves on the knucklehead Ma .... we had frawglegs last night".
EXPANDING THE USE OF OPEN TUNING VOICINGS:
NOTICE: The voicings mentioned below that are not in standard open chords, could require string gauges different from a standard set of guitar strings; But the correct string gauges are rather easy to determine by interpolating the notes of the voicing in the key you desire to tune in and matching those notes to standard guitar string set ranges in the tension you prefer (slightly heavier for Steel guitar or Slide guitar work than for fingered guitar). You can also find the correct string gauge for a given note at John Ely's Hawaiian Steel Guitar Web(site).
EXAMINING OPEN TUNING VOICING 1,3,5,1,3,5:
Allot of Pickers are distracted from fully realizing the simplicity of voicing and choosing notes therein, because the standard Guitar tuning neccessitates different fingering for each open chord ...which passively suggests an assumption that the voicings of those chords are way different, but they are not.
A 2 octave set of triads that fit right onto 6 strings, is 1, 3, 5, 1, 3, 5. This can be used for D, E and G open tuning (or of course for any roots in between). You will find that your own slide licks can be found somewhere in that voicing, but likely on differnt strings. We'll use this voicing example to compare-with in some anlysis of voicings. I will refer to this voicing as 135135. Look at the standard tuning chord voicing figures on the left of this page. We see that C chord voicing is 313513 (although 513513 works better for slide). "Standard" Drop-D voicing in open tuning is 151513 ... or E voicing dropped 1 step to D is 151351 ... or like the example comparison voicing, 135135. Open E is 151351 ... or 135135. Open G is 135131 ... or 135135. Open A is 515135. Let's look at all those voicings' numbers close together and see how many are the same in 4, 5 or 6 of the notes' sequence:
4 out of 11 have the exact same voicing sequence.
In all 11, 5 notes of the exact sequence can be played with 135135.
6 out of 11 have the exact same order but 1 note on it's end shifted to the other end.
10 out of 11 have at least 5 notes in the same sequence.
All 11 have at least 4 notes in the same sequence
All of them have at least 3 notes in the same sequence.
SO WHAT DOES IT ALL MEAN MR. NATURAL? "Twas ever meant, Chilluns"!
BUILDING THE MEANINGS SO FAR A STEP AT A TIME:
(1) Tuning voicings gives their particular character of sound to an open chord.
(2) If that voicing is found in another chord and transposed by slide to the desired pitch, it will have pretty much the same character. Obviously, licks in the same voicing would be the same anywhere on the neck.
(3) Most slide licks' utilize a group of no more than 4 adjoining strings at one time.
(4) The tuning voicing 135135 selectively contains the voicings of 11 out of 12 of the above tunings ...for licks using 4 strings !
(5) Licks using 5 or 6 strings amount to strummed chords; Sounding the same with tuning voicing 135135 as other voicings, especially by blocking either of the outside strings.
(5) The tuning voicing 135135 selectively contains the voicings of all 12 of the above tunings ...for licks using 3 strings.
(6) So it is now obvious: An open tuning voicing of 135135 will cover ALLOT more ground than any other triad tuning. A 7string Guitar tuned 1351351 ALMOST gets all voicings !
TRICKS USING 135135:
135135 is the same notes as it's relative minor. So to play Amin7 just play C.
Move 135135 up 3 frets from Major, and you get min7 (b3,5,b7,b3,5,b7). ie, to play Gmin7, play the slide 3 frets higher than G.
Similarly, there is a different fret on the guitar for some substituion voicing of EACH of the 7 common chord types (Maj7, min7, Dom7, min7b9, min7b5b9, Maj+4, dim). But no faking it here, you will have to know and choose your notes to get what you want and be able to avoid the notes you DON'T want to voice. Finger picking is good to learn to play these techniques well. CLICK HERE to learn more about playing any scale or chord by SIMPLE modal knowledge and subsitution.
HOW TO MAKE THE 135135 REPLACE ALL OF THE ABOVESAID
OPEN TUNINGS ... AND PUT YOU LIGHT YEARS AHEAD OF THEM: