it's fairly common in Africa for there to be a group of expert musicians surrounded by others

for there to be a group of expert musicians surrounded by others是不定式复合结构，在句子中做主语，相当于主语从句that there are a group of expert musicians surrounded by others

it 是形式主语，for there to be a group of expert musicians surrounded by others是真正的主语。
这种用法比较特别、以前也没怎么见过，但还是可以接受的，多熟悉下，应该就会熟练运用了。
整句翻译为：在非洲，一群音乐专家被别人围着是很正常的。

for 连接主句和从句
there to be 从句的there be句型