Scott Bradlee's Postmodern Jukebox is an ongoing musical concept project that began as one man and his piano on YouTube in 2009. It then gradually expanded an early recognisable version of its current band format in 2011, and has since exploded far beyond its original roots to become a YouTube sensation big enough to warrant three world tours so far in real life.
Postmodern Jukebox is a concept rather than a band because the "members" are constantly rotating. The concept is this: take some performers and a song (usually a modern song) and perform a cover of it in another style (usually a vintage style). The resulting video is then uploaded to YouTube, with new videos weekly. Their most popular video, which is also my personal favourite, was uploaded in April 2015 and currently has over 40 million views; a cover of Radiohead's song Creep featuring Haley Reinhart. Even new videos are popular; out of all the videos uploaded in the last month, the lowest viewed one still boasts 343 thousand views already.
Videos have a simple fixed camera view of the performing space. A decent amount of videos have background dancers, with tap dancing solos being regular. The various singers often wear vintage inspired clothing. Basic choreography and movement is considered too. Sometimes halfway through a song a band member will pop up from behind a music stand or appear from the side of the camera shot before playing. A singer might have a ukelele dropped down to them from the top of the camera shot, or pull a cloth off the hidden object next to them to reveal a trombone that they then play a solo on. A highly energetic tambourine player may wander in, see the band is playing, then join in enthusiatically. The music by itself is good and can be bought on CD or heard on various music streaming services, however I recommend watching the songs on YouTube too, as they are greatly enhanced by the various presentations given in the videos.
The "one man and his piano" who started it all is Scott Bradlee, arranger & pianist, who uploaded himself playing various songs in alternate styles to the YouTube channel ScottBradleeLovesYa. Postmodern Jukebox is said to be founded by Scott Bradlee in 2011, which is when the band format took over. Early jams happened in Scott's basement in Queens, New York, and the videos were filmed in his living room. They have since upgraded to a different venue with a slightly larger room to play in. Their live shows are excellent, with many performers, instruments, and shenanigans. When buying tickets, you are purchasing an experience of the concept, with no idea which performers will be at the show you will be watching. Members do not stay constant throughout a world tour, with some being in all the shows and some being in just one segment, such as Europe. Sometimes a perfomer will only be in a single city; I hear the energetic tambourine guy has a habit of randomly appearing in the occasional show.
Because of the fluid nature of the concept, the shows can be flexible. The second time I saw them perform live was in 2016 at the Perth Concert Hall, where a huge pipe organ is installed. At one point, the piano player appeared up above the stage where the pipe organ is, made a show of kicking off his shoes to free up his feet for the organ pedals, then went to town with several solo snippets. There was, of course, the brief occurrence of the popular organ piece Toccata, however he then played the absolute pinnacle of the night for me; an immensely rich pipe organ version of Pure Imagination, played in full in tribute of Gene Wilder who had died just one month before.
Postmodern Jukebox still uses Scott Bradlee's original channel as their YouTube home, and their website for everything from CDs to tickets is https://postmodernjukebox.com/.