Latvian language
The Middle dialect is spoken in central and Southwestern Latvia. Kursenieki language, which used to be spoken along Curonian Spit, is closely related to the varieties of middle dialect spoken in Courland. The dialect is divided into the Vidzeme variety, the Curonian variety and the Semigallian variety. The Vidzeme variety and the Semigallian variety are closer to each other than to the Curonian variety, which is more archaic than the other two. There are three intonations in the Middle dialect. In the Semigallian variety, "ŗ" is still used. Standard Latvian is based on the middle dialect.
Latgalians
They likely spoke the Latvian language, which probably became the "lingua franca" in present-day Latvia during the Northern Crusades due to their alliance with the crusaders. Latgalians later assimilated the neighbouring tribes, forming the core of modern Latvians.