Portamentos, otherwise known as pitch bends or slides, are the technique of changing the pitch of strings while they are played. On guzheng this is accomplished by pressing the string on the left side of a movable bridge.
Pitch bending is an important part of Chinese music and its history. It reflects the importance of tones in Chinese languages and traces its lineage to chanted poetry and other vocal music. Each string can slide up to three half steps above its open pitch. For example, a string tuned to G can slide G -> G# -> A -> A#.
For the sake of these descriptions, every “press” means the left hand is pressing to the left of the movable bridges and a pluck is with the right hand to the right of the movable bridges.
The famous term is Huáyīn 滑音 or “Sliding Sound” which has its own entry below. There are more specific terms as well. These cover both single direction slides and multi-direction (back and forth) slides.
The general term for a slide from one pitch to a second and then back. Kao offers two with this name:
Huiyin 1: Pluck a string, press it in with the left hand, and then relax the left hand, creating an up-down slide.
Huiyin 2: Pluck a string, press it in with the left hand, relax the left hand, and then press it again, creating an up-down-up slide. May be abbreviated to just huí 回.
Pluck then slowly press a string at the same time to slide to the next higher note, then slowly relax the left hand for a returning downward slide. Ferguson offers two variants of this: Tèshū huáyīn 特殊滑音 “Extraordinary Slide”, a slow version, and gāo huízhuǎn huáyīn 髙回转滑音 (trad. 髙回轉滑音) “High Returning Slide”, A fast version played in half the time. Kao offers the Henan term Shuāng huáyīn 双滑音 “Double Slide”.
The inverse of Shàng huí huáyīn. Press a string first. Pluck the string, relax the left hand at the same time, then press the left hand for a returning, upward slide. Ferguson offers another name for this, Dī huízhuǎn huáyīn 低回转滑音 (trad. 低回轉滑音) “Low Returning Slide”. Kao offers the Henan term Sù huáyīn 速滑音 “Fast Slide”.
Alternate notation:
Pluck a string then press it, varying the pitch in the rhythm shown on the music. Kao offers this as a Hakka technique which may be used in place of Huí huáyīn.
Pluck a string then a moment later, press the string to raise the pitch 1-3 half steps and release it. This creates a rapid alternation around a target pitch, known is western music as a mordent. It is a fast technique performed on shorter notes such as eighth or sixteenth notes. Kwok considers it a vibrato, offers the synonym shuanq rouyin and says the strong should be pressed twice.
A type of returning portamento. Pluck a string then bend it to slide down-up-down or, bend a string then pluck it for an up-down-up series of slides. To quote Han 2013: “Nao is very effective in expressing gentle, sad, or elegant emotions. Although it is used in all styles, southern styles are particularly famous for applying it.” It is meant to evoke the motions of a type of monkey, a secondary meaning of the character.