指弹玩到一定程度，会进入进阶学习的阶段，这之中特殊调弦式弹奏是一个需要下功夫研究的非常重要的内容。因为有的和弦在标准调弦上很难按出，更别说能够流畅演奏，而用了特殊调弦，原来难按的和弦变容易了，这就更有利于演奏者发挥自己的想法，弹出更动听的音乐。
特殊调弦分两类，即变化调弦 (Alternative Tuning) 与开放式调弦 (Open Tuning)
变化调弦是在标准调弦的基础上，在某根弦作变动，或整体升高或降低整个调弦音调；而开放式调弦则是一整个调弦的空弦音就是一组和弦。
所以，比如说灌蓝高手，这个就是变化调弦，为什么？因为它只是在标准调弦上稍稍做了改动。
而大家所熟知的 Wings You are the Hero 则是开放式调弦, DADGAD 六根弦构成了 Dsus4 和弦。
特殊调弦不是我们想像中那种就调调弦的音高这么简单，有时要用特殊的弦，有的时候使用某个特殊调弦，考虑到其对琴体的伤害，甚至要对琴体的设计进行调整！！
以下是我收集并翻译的一些资料，供各位琴友参考：
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Alternative Tuning 变化调弦
Alternative tuning refers to any open string note arrangement other than that of standard tuning detailed above. Despite the usefulness and almost universal acceptance of standard tuning, many guitarists employ such alternative tuning arrangements in order to exploit the unique chord voicing and sonorities that result from them. Most alternative tunings necessarily change the chord shapes associated with standard tuning, which results in certain chords becoming much easier to play while others may become impossible to play.
变化调弦指的除上述标准调弦外的任何一个空弦的变化组合。虽然标准调弦用处很大，而且几乎是一个通用的标准，很多吉他手仍然用变化调弦来开发独特的和弦音及其产生的明亮音色。大部分变化调弦必需调整标准调弦有关的和弦形态，这样会产生某个和弦很容易演奏，而其他的和弦就有可能变得无法弹出来的情况。
As a standard set of guitar strings is designed to be tuned to the standard notes, alternative tunings may require not just a different tuning, but re-stringing of the guitar with strings better suited to the open string note. In turn, further adjustments to cope with the different tensions placed on the guitar may be required, and in extreme tunings, fitting different components to cope with the different gauges used.
由于吉他标准套弦都是为标准调弦音所设计的，变化调弦可能不仅仅是改变一下调弦，还可能要重新设计吉他的琴弦以使其更加适应发出空弦音。同样为了应对吉他所受的不同张力而做一些调节也是必要的，在一些极端的调弦法里，还会用到一些不同的组件来应对不同型号的弦。
Rock music Tunings
Guitar tunings in rock music and metal are employed in order to make power chords easier to play and/or to make the sound “heavier”.
摇滚乐调弦
在摇滚乐及金属乐中，使用此种调弦以便更容易按出强力和弦，也使得声音更有“劲”。
Dropped D: D-A-D-G-B-E’
This tuning is not only used by metal and rock bands, but also folk musicians. It allows power chords (also known as bare fifth chords) to be played with a single finger on the lowest three strings. It is also used extensively in classical guitar music and transcriptions since it allows open strings to sound the tonic and dominant as part of the bassline in the keys of D and D minor. Some guitarists choose to use a capo on the second fret with this tuning so that they can retain the ease of playing power chords without the darker sound created by the D tuning.
降 D: D-A-D-G-B-E’
此调弦不仅于金属及摇滚乐队用，民谣乐手也用它。它使强力和弦（也称横5和弦）用一根手指按在后面三根弦上就可以按出来了。它同时也在古典吉他音乐及典藉中被广泛使用，因为它可以在 D 大调及 D 小调中的低音进行中使空弦音的更浑厚有力。一些吉他手在用这个调弦时，用一个变调夹夹在第二品，这样他们可以保证强力和弦易按性的基础上，不致让音色因使用 D 调弦而变得黯淡。
Dropped C: C-G-C-F-A-D’
This tuning is the same as dropped D, but each string is lowered an additional whole step, or two semitones. Technically a “drop C” tuning would be C-A-d-g-b-e’. However, the tuning technically known as “Dropped D tuned down one whole step” is commonly referred to as “Dropped C” tuning, as very few people drop only the sixth string. This gives the guitar a very low and heavy sound, and usually requires extra-thick strings to maintain tension. This tuning is frequently used by hardcore and metalcore bands as well to achieve a lower sound. Tuning a standard, non-baritone guitar any lower than this is difficult.
降 C： C-G-C-F-A-D’
这个调弦与降 D 调弦是一样的，但每根弦都多降了一个全单，即两个半音。其实降 D 可以是C－A－D－G－B－E。不过技术上来说，降 D 向下调一个全音即是降 C 调弦，因为很少人只是调一下第六弦。此调弦赋于吉他一个非常低且重的音色，经常要用特粗的弦来保持弦紧。此调弦常会被一些重型音乐，金属音乐的乐队所用来达到低音效果。很难将一把标准的，非低音吉他调得比这个调弦更低。
Dropped B: B-F#-B-E-G#-C#’ or B-Gb-B-E-A-D’ or Bb-Ab-Db-Gb-Bb-Eb
This tuning is the same as dropped D and C, but lowered from dropped C an additional semitone, or half step. This tuning is very popular with alternative metal/post-grunge bands. It has also become popular with doom metal/post-metal bands. Heavier gauge strings are required for this tuning, which may also require widening the string grooves in the nut of the guitar as well as re-adjusting the tension in the neck.
降 B 调弦：B-F#-B-E-G#-C#’ 或 B-Gb-B-E-A-D’ 或 Bb-Ab-Db-Gb-Bb-Eb
这个调弦与降 D 降 C 也是一样的，但是在降D的基础上降了半音。这个调弦在金属及前 GRUNGE 乐队中很受欢迎。它也在末日金属及前金属乐队中很受重用。这种调弦要用到更粗的弦，这样就需要加宽琴枕上的开槽，还要重新调节琴颈的强度。
Dropped A: A-E-A-D-F#-B or A-A-D-G-B-E’
A very low drop tuning used in metal and death metal bands. As with the Dropped B tuning, heavy gauge strings are required, and even minor modifications to some guitars. The second version (A A D G B E) has been used by Thrice in songs such as “The Earth Will Shake” and “Firebreather and Nile as their main tuning.”
降A调弦A-E-A-D-F#-B 或 A-A-D-G-B-E’
金属及死亡金属用的一种很底的调弦。跟降 B 调弦一样，需要装特粗的弦，甚至要对吉他进行一些小的改造。Thrice 在歌曲“大地震颤”及“吸火人”，“尼罗河”的主调弦中使用了这个调弦。
Eb tuning: Eb-Ab-Db-Gb-Bb-Eb’
This tuning is achieved when all the strings are flattened by a half step. This can be combined with other tuning techniques such as dropped D tuning and makes no difference to fingering. Often the key will be considered by the players as if played in standard tuning. This tuning can be used for a number of reasons: to make larger strings bend more easily, to make the tone heavier, to better suit the vocalist’s range, to play with saxophone family more easily, or to play in E? pentatonic minor formed by the black keys of a keyboard.
降 E 调弦：此调弦是将所有的弦降一个半音。可以与其他调弦技巧如降 D 调弦等一同使用，在指型上不需做出变化。通常演奏者在根音上把它看作与标调一样。此调弦的使用基于以下几个原因：更好地在粗弦上推弦，加重音色，更好地适应歌手的音域，更容易与萨克斯一同演奏，弹奏键盘黑键形成的五声小调。
The tuning was made famous by Jimi Hendrix who used it extensively during his career and on all songs after Are You Experienced. Guns N’ Roses also favoured E flat tunning because it allowed Axl Rose’s voice to be accentuated on the high notes. It is also used by Metallica to compliment James Hetfield’s voice.
因 Jimi Hendrix 在其音乐生涯中大量的使用这种调弦，且在《在你经历了以后》这个曲子后所有的曲子都是用这个调弦，从而使得这个调弦声名大噪。枪与玫瑰也是用降 E 调弦润色，这样使得 AxlRose 的嗓音可以着重在高音上表现，同时 Metalica 也用这个调弦来衬托 Gakoo 的嗓音。
D tuning D-G-C-F-A-D’
Also known as “One Step Lower” and “Whole Step Down”, this tuning is basically E Standard with all six strings tuned one whole step down. Although mostly utilized in heavy metal, one sometimes find this tuning in Blues, where guitarists use it to accommodate string bending.
D 调弦 D-G-C-F-A-D’
也称作“低两格”或“低全音”，这个调弦是在 E 标准调弦的基础上调低一个全音，虽然大都是重金属才使用它，有时候也可以在布鲁斯里看到这个调弦，这里吉他手用它来适应推弦。
C tuning: C-F-Bb-Eb-G-C’
C standard tunes the strings of the guitar to produce a low tone. This tuning is commonly used by metal and hard rock artists as it is two whole steps below standard tuning. This tuning can also be written as C-F-A?-d?-g-c’. It allows for a low, heavy sound, while still maintaining the intervals present in standard tuning.
C 调弦 C-F-Bb-Eb-G-C’
C 调弦将吉他的弦调出一种很低的音色。这个调弦被金属及硬摇滚的音乐人所用，它比标准调弦要低两个全音。这个调弦也可以记作：C-F-Bb-Eb-G-C’，它可以弹出又低又重的声音，同时又保留了标准调内部指法。
B tuning:
Also known as “B Standard” or “Baritone” tuning, this tuning is a common tuning of seven-string guitars, which are tuned B,E,A,D,G,B,E. On a six string guitar, the tuning is modified to B,E,A,D,F#,B.
B 调弦，也叫“B 标准调弦”或“低音调弦。这个调弦是七弦琴的一个很普遍的调弦，各弦音为 B,E,A,D,G,B,E，在六弦的吉他上，这个调弦改为 B,E,A,D,F#,B.
Bb tuning:
Takes B Standard on either a six or seven string guitar down a semitone (or half step). For example, bands such as Nevermore of the progressive metal genre utilize this on seven string guitars. The tuning result is (from low to high) Bb, Eb, Ab, Db, Gb, Bb, Eb.
降 B 标准调弦在七弦或六弦琴上调低一个半音，如 Nevermore 的金属改革流派就在七弦琴上用这种调弦。这个调弦从低到高依次是 Bb, Eb, Ab, Db, Gb, Bb, Eb.
However, on a six string guitar (from low to high) it would be Bb, Eb, Ab, Db, F, Bb.
不过在六弦的吉他上（从低到高）为：Bb, Eb, Ab, Db, F, Bb.
