I've mentioned Johnson a couple of times on Mudcat. Lang took a nickname to disguise the fact that he was white. It wasn't done for black and white musicians to record together. I mentioned Johnson's 'duets' with Victoria Spivey. Lonnie Donegan is said to have got the 'Lonnie' from Lonnie Johnson. Johnson's career had several parts. Along with Spivey he had a come-back career in the 70s. Some of the lyrics from their earlier songs are worth a look. Johnson is said to have been a pioneer of the guitar solo, but he was also rated as a singer. He played different styles through his career. He does several versions of 'Careless Love' and the phrasing in the 1965 one is magnificent.