Proposal to add Chinese repeat ad lib. sign

[LupusCaeruleus]

(This proposal comes from the discussion in #172)

I would like to suggest adding the Chinese repeat ad lib. sign.

The appearance of the Chinese repeat ad lib. sign is basically two circles located in the center of a horizontal bracket, and, as the name suggests, the segment of music within the bracket is to be played as many times as the player wants.

I have no idea when or where this sign originated, but it is commonly used in many traditional Chinese musical works (and their arrangements for western instruments) since the 1970s, and can also be found in relatively recent publications. Here are some examples:

1. Revolutionary Modern Peking Opera, Taking Tiger Mountains by Strategies, Full Score (革命现代京剧 智取威虎山 总谱), by Shanghai Peking Opera Troupe (上海京剧团), published by People‘s Publishing House (人民出版社) in Aug 1970.
   

2. Ambush from All Sides (十面埋伏), by Chengzong Yin (殷承宗) et al, published in 1973. (Sorry, I was not able to find the publisher)
   

3. A Moonlit Night on the Spring River (春江花月夜), by Meizhen Wang (王梅贞), from Collection of Works for National Electronic Keyboard Performance Examination (全国电子琴演奏考级作品集), published by Xinhua Publishing House (新华出版社) in 1999.
   

4. An Evening in Autumn (秋夜), by Eugene Kuo (郭豫椿), from Collection of a Century of Chinese Music, Vol. 5 (中国音乐百年作品典藏 第5卷), published by People‘s Music Publishing House (PMPH, 人民音乐出版社) in 2014.
   

5. A note on the sign in the book the Teng Guide to the Chinese Orchestra, by Chenwei Wang et al, published by World Scientific Publishing Co. Pte. Ltd. in 2020.
   

6. Ambush from All Sides (十面埋伏), by Hong Kong Chinese Orchestra (HKCO), 2023.
   The full score and part scores can be accessed here on HKCO's official website.
   

Personal suggestions for the inclusion:

Though the Chinese repeat ad lib. sign can be easily recreated using many other characters or symbols (like the capital letter “O” or the circle “○”), it is still necessary to add it as a unique symbol, since it has a special meaning and requires a consistent appearance.

Considering the way that the tuplet numbers (U+E880–U+E88F) are currently encoded in SMuFL, I would suggest only the two circles be defined as the Chinese repeat ad lib. symbol, and the bracket should be drawn using primitives in scoring applications. In addition, I would suggest placing the Chinese repeat ad lib. symbol within the Repeats block, given its meaning.

If the musical term ad lib. is not an appropriate name, other synonyms can also be used, e.g., Chinese Repeat Arbitrarily.

[mscuthbert]

This looks like a well-used, well-documented symbol with good suggestions for how to add. Maybe with name repeatAdLibChinese -- putting the meaning first and the country of origin last, since (having no concise equivalent in other countries) its usage may spread.