Minstrel banjo was what's called "stroke style", of which frailing or clawhammer is a subset.

Along about the beginning of the 20th Century, as the music that was popular started to change, there was a TREMENDOUS fad for the tango. The 5-string banjo didn't fit into that kind of beat. There was developed what was called the tango banjo--four strings, short neck, played with a plectrum. It worked well for traditional jazz, too. We call it the tenor banjo today.

Dave Oesterreich