Czech Lullabies
In the Czech language a lullaby is called ukolébavka which is derived from the verb kolébat, meaning to rock-a-bye. Rocking of the cradle or the baby in arms was accompanied by quiet monotonous singing, usually by the baby’s mother. Most Czech lullabies have a limited tone range and a regular rhythm, often there is used repetition of simple recitative motifs. Though the Czech Republic is small, there is a noticeable difference between lullabies from Bohemia which is the western part of CR and those from Moravia, the eastern part of CR, especially in the east and south-east of Moravia. While Moravian lullabies are often just ditties based on two or three tones, some Bohemian are melodically more complex. Many lullabies in Bohemia are based on major triads, in Moravia the interval is treated more freely. Many lullabies exist in several versions which might differ in dialect, word choice, word order, or sometimes slightly in melody. In the eastern parts of Moravia neighbouring with Slovakia there are several regions where the folklore is still alive, where people, at least the older generations, sing more, including lullabies.
In the 19th century, especially during the Czech national revival, there were several collectors of folk songs including lullabies, such as K. J. Erben, F. Sušil and F. Bartoš, who collected thousands of songs from the country people. One of the most beautiful and best known folk lullabies Hajej, můj andílku was used by Czech composer B. Smetana in his opera The Kiss. He also composed one more lullaby entitled Letěla bělounká holubička for this opera. Another Czech composer L. Janáček arranged and used the lullaby which appeared as early as 1633 when Comenius, Czech theologian and pedagogue, included it in The Informatorium of the School of Infancy, the first European systematic programme concerning the aims and methods of pre-school education. Several 20th century composers reworked folk lullabies or created new ones, using often the texts of acknowledged poets, for example of Jaroslav Seifert, the Czech poet awarded the Nobel Prize in 1984. However, these lullabies are much less known and rather than for soothing children to sleep they are exploited by choirs who sing them at concerts.
Czech lullabies usually open with expressions such as spi, spinkej, hajej, dadej, nynej, halí, belí, halaj, belaj, buvaj (all pronounced in the same way as spelled with the exception of j which is pronounced as English y). Most of these words belong to baby talk or motherese, all meaning imperative of the verb sleep. Still, they differ slightly:

spi is a neutral expression
spinkej is diminutive of spi, used for children or beloved
dadej, nynej used in Bohemian lullabies
belaj, buvaj used in lullabies from eastern Moravia
hajej means also lie or keep lying, used in Bohemian lullabies
hali, halaj similar to hajej, the latter used in eastern Moravian lullabies

As for the content of lullabies, the baby is often promised something if s/he sleeps nicely: apples, pears, raspberries, something yummy, a hat, a drum, a falcon etc. Less frequently there is a threat of some punishment for being awake and crying: I’ll rock you off the cradle, I’ll throw you into a pond. In some lullabies the expected threat turns into the promise of a gift: I’ll leave you, I’ll leave for the garden to pick plums. Very often the baby is being assured of mother’s love, or of the care of little angels, i.e. cherubs while asleep, and sometimes also Pámbů, which is a familiar form of God or Lord.