What does it mean to travel in the sky?

People often confuse northern Shaanxi folk songs with northern Shaanxi's belief in heaven. In fact, folk songs in northern Shaanxi are irreplaceable by Xintianyou in northern Shaanxi. Folk songs in northern Shaanxi are a big concept, including northern Shaanxi's belief in heaven. Xintianyou in northern Shaanxi is only a special genre of folk songs in northern Shaanxi, and it may also be the most distinctive and representative genre of folk songs. Like other Yuefu poems and folk narrative poems, northern Shaanxi folk songs have no strict restrictions on sentence structure, and each paragraph can be three, four or even five or six sentences. However, Xintianyou in northern Shaanxi is not like this. There are only two sentences in each section, which rhyme. You can change the rhyme in the next section. If you don't change it, you must rhyme to the end, and you can't make a free poem without rhyme. Li Ji's famous long poem Wang Gui and Li Xiangxiang was written in the form of epistolary tourism. He Jingzhi's Back to Yan 'an is also a model of imitating the belief in Heaven. However, the folk songs in northern Shaanxi, which are well-known to Chinese people like Dongfanghong, cannot be described as believing in heaven, and no one can classify it as believing in heaven.