You've heard of twin guitars and twin fiddles in Western Swing, how about twin (electric) mandolins!
This is Al Dressen's Super Swing Revue performing Johnny Gimble's tune "Mandolopin'" with Jason Roberts and Paul Glasse on mandolin. It was recorded at the 18th Annual Texas Natural & Western Swing Festival held on May 15 2010 in San Marcos, Texas.
The mandolin is typecast as a bluegrass instrument, but it actually has lots of versatility. Electric mandolin, while not an essential instrument in Western Swing, have a long history in the genre. Most famously, Tiny Moore began playing a Gibson electric mandolin with the Bob Wills band in 1946. Instead of using the eight strings of the standard mandolin (four courses tuned in unisons), Moore used only four strings. In the 1950s, Moore, playing in Billy Jack Wills' band, commissioned a 5 string electric mandolin from Paul Bigsby. Before Moore, Leo Raley played electric mandolin in the 1930s with the Western Swing band of Cliff Bruner, most likely the first electric mandolin. The legendary Johnny Gimble, composer of the tune featured above, played electric mandolin and violin with the Wills band. There was an overlap in their tenure and there must have been some twin mandolins. Most likely, the Tiffany Transcriptions captured some of this.
Here's a picture of Moore (second from right) with Bob Wills from the early 1950s. There is another mandolin player, possibly Gimble to Moore's right. (Photo is from Musings Of A Muleskinner--Deke Dickerson's Blog.)
Because the mandolin is tuned identically to the violin, many Western Swing double on the two instruments.