Which ancient musical instrument is referred to by the "willow leaf zither, vajra leg, and earth lute"?

Liuqin, stringed instrument. Also known as willow leaf qin, vajra leg, soil pipa. It is a traditional Han Chinese musical instrument. Originally popular in Suzhou, Lu, Anhui and other provinces. Now popular in all parts of the country, to Shandong Linyi and the northern part of Suzhou. It is one of the pear-shaped speaker stringed instruments that have been passed down in the folklore since the Tang Dynasty, and its shape, structure and playing method are similar to that of Ruan. The earliest liuqin, the structure is very simple, due to the appearance of the liuqin earthy, very folk, the Chinese people affectionately called it "soil pipa".

The liuqin was used as an accompaniment to liuqin opera, sizhou opera and other local operas, as well as to play simple songs, with a loud and grand pronunciation, a high and strong tone, and a rich local flavor. After a long period of development, it has developed into a solo instrument and is often used as a soprano instrument in ethnic bands.

The liuqin is suitable for playing cheerful, contrasting, rhythmic, elastic and lively tunes, as well as beautiful, lyrical melodies, and can work harmoniously with pipa, ruan, zheng and erhu in the orchestra.

The liuqin also has the acoustic effect of the mandolin, which is more flavorful when it cooperates with the Western orchestra, and can be blended and complimented in terms of timbre. In the folk band - Changzhou Silk String, the liuqin can work closely with the flute as the main player, and play the role of accompaniment, enhancement of contrast and decoration. In the instrumental ensemble, sometimes it is also in the leading position, which can well regulate the change of tone color.