To the untutored ear, the Beijing dialect can sound like someone talking with a mouthful of marbles, inspiring numerous parodies and viral videos. Its colourful vocabulary and distinctive pronunciation have inspired traditional performance arts such as cross-talk, a form of comic dialogue, and "kuaibanr", storytelling accompanied by bamboo clappers.

But the Beijing dialect is disappearing, a victim of language standardisation in schools and offices, urban redevelopment and migration.

In 2013, officials and academics in the Chinese capital began a project to record the dialect's remaining speakers before it fades away completely. The material is to be released to the public as an online museum and interactive database by year end.

"You almost never hear the old Beijing dialect on the city streets nowadays," said Mr Gao Guosen, 68, who has been identified by the city government as a "pure" speaker. "I don't even speak it anymore with my family members or childhood friends."

The dialect's most marked characteristic is its habit of adding an "r" to the end of syllables. This, coupled with the frequent "swallowing" of consonants, can give the Beijing vernacular a punchy, jocular feel. For example, "buzhidao", standard Chinese for "I don't know", becomes "burdao" in the Beijing dialect. "Laoshi", or teacher, can come out sounding "laoer".

In the 1930s, China's Republican government began defining and promoting a common language for the country, referred to in English as Mandarin, that drew heavily, but far from completely, on the Beijing dialect. The communist government's introduction of an official Romanisation system in the 1950s reinforced standardised pronunciation for Chinese characters. These measures enhanced communication among Chinese from different regions, but they also diminished the relevance of dia

A 2010 study by Beijing Union University found that 49 per cent of local Beijing residents born after 1980 would rather speak Mandarin than the Beijing dialect, while 85 per cent of migrants to Beijing preferred that their children learn Mandarin.

The remaking of the city has also played a role in diluting the language. Into the mid-20th century, much of Beijing's population lived clustered in the hutongs, or alleyways, that crisscrossed the neighbourhoods surrounding the Forbidden City.

Today, only a small fraction of an estimated 3,700 hutongs remains, their residents often scattered to apartment complexes on the city's outskirts. And the city has become a magnet for migrants from other parts of China. According to China's last national census, an average of about 450,000 people moved to Beijing each year between 2000 and 2010, making about one-third of Beijing's residents non-locals.

Mr Gao, a diminutive man with a booming voice, remembers how different it used to be.

"Until this project, I didn't even know that what I was speaking was a dialect, because everyone around me used to speak like that," Mr Gao said in his new apartment, not far from the hutong where he lived for more than 60 years.

According to the United Nations, nearly 100 Chinese dialects, many of them spoken by China's 55 recognised ethnic minorities, are in danger of dying out. Efforts are also under way in Shanghai, as well as in Jiangsu and five other provinces, to create databases as part of a project under the Ministry of Education to research dialects and cultural practices nationwide.

Yet the potential loss of the Beijing dialect is especially alarming because of the cultural heft it carries.

"As China's ancient and modern capital, Beijing and thus its linguistic culture as well are representative of our entire nation's civilisation," said Professor Zhang Shifang at the Beijing Language and Culture University who oversaw the effort to record native speakers. "For Beijing people themselves, the Beijing dialect is an important symbol of identity."

The dialect is a testament to the city's tumultuous history of invasion and foreign rule. The Mongol Empire ruled China in the 13th and 14th centuries. The Manchus, an ethnic group from north-east Asia, ruled from the mid-17th century into the 20th. As a result, the Beijing dialect contains words derived from both Mongolian and Manchurian. The intervening Ming dynasty, which maintained its first capital in Nanjing for several decades before moving to Beijing, introduced southern speech elements.

The dialect varied within the city itself. The historically wealthier neighbourhoods north of the Forbidden City spoke with an accent considered more refined than that found in the poorer neighbourhoods to the south, home to craftsmen and performers.

In Shanghai, some schools teach in Shanghainese rather than Mandarin. The Beijing city government has explored the idea of developing teaching materials in the Beijing dialect. However, these proposals have been criticised by those who fear such lessons would diminish the effectiveness of Mandarin-language education.

"As a Beijing native, I personally hope the dialect will survive," said teacher Wang Hong at the Affiliated Elementary School of Peking University. "But if you aren't a native, there's no reason to learn Mandarin plus a dialect. You would just confuse the two."

The researchers documenting the Beijing dialect are quick to stress the preservationist nature of their efforts.

"We aren't promoting the teaching of dialect in school, because China is still a Mandarin-speaking society," said Mr He Hongzhi, the director of the forthcoming online dialect museum, which will showcase some of the recordings collected by Prof Zhang.

For Mr Gao, the vanishing dialect of his youth is nothing to be mourned, although he is happy that more people are paying attention.

"Society needs a unified language and culture to develop," he said. "If we restored the old things, then the road ahead wouldn't exist."

He added: "But I love to listen to the Beijing dialect. It is something innate. When I speak the Beijing dialect, it comes naturally from my heart."

NYTIMES