This tuning uses quite a few different names. Melodies that use the tuning include:

1. Shenpin Guxian Yi (present melody)
2. Feiming Yin (Shen Qi Mi Pu #63: probably a prelude to #64, Qiu Hong)
3. Qiu Hong (conveys the same idea as #63 and, with 36 sections, the second longest piece in the qin repertoire)
4. Jiazhong Yi (modal prelude; 1549) and the two pieces that follow it:
5. Yueshang Yin and
6. Yueshang Cao
7. Nanlü Yi (1571) and the melody that follows it:
8. Qiu Sheng (1571); seems to be a condensed and adapted version of Qiu Hong
9. Dao Yi (1589); lyrics, but unrelated to Dao Yi Qu
10. Ming De Yin, serving as a prelude to:
11. Kong Sheng Jing (both Confucian hymns; mode called biyu, but no modal prelude)

The Table of Contents adds "same as Defining Qingshang",⁴ while below the mode name, before the modal prelude, is the following explanation:

This is a purely pentatonic tuning, so the normal harmonic relationships apply. In this case harmonics on the seventh position of the 6th, 5th and 4th strings have the same pitch as harmonics on the ninth position of the 3rd, 2nd and 1st strings respectively; and harmonics on the ninth position of the 7th, 6th, 5th and 3rd strings have the same pitch as harmonics on the tenth position of the the 5th, 4th, 3rd and 1st strings respectively.⁶

As shown above, Longhu Qinpu also has this tuning, calling it nanlü;⁷ note that in 1549 the tuning for nanlü is different.

There are 24 modal preludes using this tuning (including those under the names guxian, qingshang, jiazhong, gu jiazhong and nanlü) identified in 20 handbooks from 1425 to 1722.⁸ In all the modal preludes the main note is 1 (gong; open 2nd and 7th strings), often accompanied by 5 (zhi). Sometimes 6 (yu) and 3 (jiao) are secondary tonal centers. This is also true of the two SQMP melodies that use this mode.

As with mangong, the stated tuning method required retuning three strings, in this case up instead of down. However, if one normally tunes the strings as high as they comfortably can go without fear of breakage, then this tuning must be accomplished by lowering four strings (1, 3, 4, 6) instead of raising three.

Perhaps the inconvenience of having to retune so many strings is the main reason for the fact that, although guxian as a note and as a mode have an ancient history, since the Ming dynasty it has not much been used much: for the repertoire that survived into Qing dynasty handbooks, this tuning is associated only with the two pieces included here in Shen Qi Mi Pu, plus the Dao Yi first published in 1589.

 
No commentary ⁹

 
One section

(00.50) -- harmonics
(01.07) -- Modal prelude ends

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Footnotes (Shorthand references are explained on a separate page)

1. Celestial Air Defining Guxian Mode (神品姑洗意 Shenpin Guxian Yi Guxian is the fifth of the 12 pitches (lü), corresponding to E in a scale from C to C' (6286.19 姑洗：十二律之一 ....[國語，周語）姑洗所以脩潔百物考神納賓。]). It is not clear why this name is applied to this particular tuning.
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2. Guxian mode 姑洗調
For more information see Modality in Early Ming Qin Tablature. For more on modes in general also see Qin Tunings, some theoretical concepts.
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3. Tuning method: tighten 2nd, 5th and 7th strings
To achieve the same relative tuning (6 1 2 3 5 6 1) one can also loosen the 1st, 3rd, 4th and 6th strings; see above.
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4. Same as defining Qingshang
即清商意 18003.383 五音之一; also autumn wind and a spirit name. See also in Qinshi Bu (琴史補), #39 the biography of Zhong Changtong (仲長統) which says that according to Later Han History he played a beautiful Qing Shang qin.
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5. Same as Gu jiazhong mode
與古夾鐘同 . For jiazhong, 5997.97 夾鍾 and .103 夾鐘 seem to be same. Old note names. "pinched/lined/secret bell"
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6. Harmonic relationships
I don't know if this is specified in any period handbooks. This tuning method produces Pythagorean note relationships for the open strngs.
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7. nanlü; 南呂 (1571)
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8. Tracing Guxian Yi (and other modal preludes with the tuning 6 1 2 3 5 6 1)
See appendix below. Zha Fuxi's Guide has seven entries for modal preludes for this tuning. However, of the 24 individual examples indexed (from 20 handbooks), 22 are closely related either to the melody in 1425 or to the one in 1546a. The other two (1556 and 1571) each occurs only once, and the first of them seems borrowed from another tuning.
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9. Although SQMP modal preludes have no prefaces, those in Zheyin (which all have identical music) do. In Zheyin the preface to the guxian modal prelude is as follows:

Appendix: Chart Tracing Shenpin Guxian Yi (plus other modal preludes with the tuning 6 1 2 3 5 6 1)
Zha Fuxi's Guide has seven relevant entries, but there are only 4 different melodies below (see comment)

Shenpin Guxian Yi (10/--/--) Guxian Yi (12/122/215) Miaopin Qingshang Yi (18/--/--) Nanlü Yi (22/--/00) Jiazhong Yi (22/--/--) Qingshang Diao (30/236/442) Qingshang Yi (28/--/--)

琴譜     (year; QQJC Vol/page)	Further information (QQJC = 琴曲集成 Qinqu Jicheng; QF = 琴府 Qin Fu)
1.  神奇秘譜       (1425; I/164)	SPGXY; "same as 古挾鍾 Gu Jiazhong";  begins with open 4th string then 2nd stopped at 11th hui
2.  浙音釋字琴譜       (<1491; I/219)	GXY (no Shenpin, otherwise commentary same as 1425)  music also same as 1425 but adds lyrics
3. 風宣玄品       (1539; II/305)	SPGXY (same as 1425)  no commentary or alternate title
4. 梧岡琴譜       (1546a; I/434)	MPQSY (different melody);  begins with open 7th strings then 4th stopped between 8th and 9th hui
. 梧岡琴譜       (1546b; I/434)	SPGXY (same as 1425 except a few notes)
5. 琴譜正傳       (1561a; II/476)	MPQSY (=1546a)
. 琴譜正傳       (1561b; II/476)	SPGXY (=1546b)
6. 西麓堂琴統       (1549a; III/195)	GXY (same as 1425 except a few notes)
. 西麓堂琴統       (1549b; III/220)	JZY (almost same as 1546a except closing harmonics)
7. 步虛僊琴譜       (1556; Fac/51)	QSY; before Feiming Yin in facsimile edition; not in QQJC; different melody from above: begins on open 1st, 2nd then 4th strings, 2nd string 11th hui, then open 4th (compare Shenpin Qiliang Yi)
8. 太音傳習       (1552; IV/157)	GXY, but like 1546a
9. 太音補遺       (1557; III/399)	Guxian Diao Kao; almost same as 1425
10. 龍湖琴譜       (1571; 琴府/272)	NLY; different melody from all the above; precedes Qiu Sheng;  Begins open 2nd, open 7th, 2nd at 11th hui, open 4th
11. 玉梧琴譜       (1589; VI/95)	SPGXY; almost same as 1425
12. 真傳正宗琴譜       (1589; VII/217)	QSD; similar to 1546a but adds lyrics (see also 1692);  lyrics begin: 商秋，金風落葉也，草木含愁....
13. 琴書大全       (1590a; V/527)	MPQSY; like 1546a
. 琴書大全       (1590b; V/527)	SPGXY; almost same as 1425
14. 文會堂琴譜       (1596; VI/274)	QSY; like 1546a
15. 藏春塢琴譜       (1602; VI/444)	SPGXY; almost same as 1425
16. 陽春堂琴譜       (1611; VII/410)	GXY; like 1546a
17. 羲軒琴經       (late Ming; IX/444)	QSY; like 1546
18. 琴苑新傳全編       (1670; XI/444)	SPGXY; same as 1425; note under mode name says "same as JZ, i.e., QS";  is this why Zha incorrectly lists them separately as SPGXY, GXY and QSD?
19. 琴譜析微       (1692; XIII/145)	QSD; last piece; music like 1589, but lyrics (商秋...) are before the melody, not paired;  TOC suggests Shang Qiu as title, but not in Zha Guide;  stands alone as a separate melody
20. 臥雲樓琴譜       (1722; fac/V)	QSD; last piece; identical to 1692

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