LE♂N is an English VOCALOID developed and distributed by Zero-G Limited, and was released in January 2004 for the first VOCALOID engine. He, along with L♀LA, were among the first voice banks to be commercially distributed. LEON is advertised as a "virtual male soul vocalist modeled on a real professional singer"; his voice provider has never been revealed.
LEON's boxart was standard for his day and rival software package Cantor would later adopt the same boxart style, the boxart for both products are from stock images. The photographer for LEON's boxart is unknown, but the photograph is on various stock photo sites. An example of the original is here titled "Profile of woman with finger next to lips" x13037575. LEON has since been taken as one of the few "Avatar-less" VOCALOIDs.
LEON and LOLA received standard advertisement for their day. They were advertised on the internet and in electronic magazines. At the time, this was normal for software synthesizers and there was no Vocaloid fandom to aid with their development. They were aimed at professionals and therefore, had no fan input in mind.
For a period he, along with LOLA and MIRIAM, were not for sale due to the lack of interest in synthesized voices. This lack of interest was owed to the sudden change in indie music trends. After increased interest began to occur in VOCALOID™ and demand was renewed, Zero-G began reselling LEON, LOLA, and MIRIAM from their own website via their virtual shop. According to Zero-G interview in 2010, the three may also get a redesign in the future.
It is unknown how many units were sold, but as KAITO was the only commercial VOCALOID failure reported, it is safe to say he sold at least 1,000 units. According to Crypton Future Media, Leon, along with Lola, failed to impact the American market due to the "British" accents.
As there was not much of a Vocaloid fandom to begin with, most fan responses to him were given relatively late. LEON did not become popular with the public until a relatively unknown Nico Nico Douga user posted a video of him singing song "True to my Heart". This featured LEON in an unusual looking fan design which soon struck the funny bone of Nico Nico users and the video eventually received over 50,000 views.
"True to my Heart" by ちょいワル（旧垢） ft. LEON, MEIKO, Miku, Rin/Len Notice, original solo no longer available. Niconico
Until BIG AL in 2009, no other English-capable male VOCALOID existed, so those wanting a masculine vocal in the English engine had LEON as the only option.
In the Nico Nico Douga International VOCALOID ranking 2010, LEON had the 3rd most notable number of appearances, with 4 appearances in the top 30 songs of 2010.
"海外組VOCALOIDランキング2010（仮）" by あっちゃん ft. English VOCALOIDs Niconico
An independent search on Nico Nico Douga revealed that most VOCALOIDs had less than 1,000 videos uploaded on Nico Nico Douga in 2011 between July 1st and December 15th. LEON fell into that category.