Question: Ylvis recorded the music video for the song that was the top trending video on YouTube for which year?
Context: "The Fox (What Does the Fox Say?)"  is an electronic dance novelty song and viral video by Norwegian comedy duo Ylvis.  The top trending video of 2013 on YouTube, "The Fox" was posted on the video-sharing website on 3 September 2013, and has received over 690 million views as of August 2017.  "The Fox" peaked at the top of the Norwegian Singles Chart and was hugely successful in the United States, where it peaked at number six on the "Billboard" Hot 100 for three consecutive weeks, and was, before the US release of "Am I Wrong" by Nico & Vinz, the highest-ranked song by a Norwegian artist on the chart since A-ha's number-one song "Take on Me" in 1985. "Midnight Sun" is a song recorded by the Romanian female singer Elena Gheorghe.  The song was recorded in summer 2010 and premiered on November 15, 2010, on Gheorghe's official YouTube channel.  It was released under Cat Music exclusively in Romania.  The song has more house influences than the previous number-one hit "Disco Romancing".  It was sent to the mainstream radio stations in late November and it is promoted as the second single taken from Gheorghe's album entitled "Disco Romancing".  Lyrically, the song describes the shiver a millionaire wannabe guy gets when he sees Elena dancing.  The song had its official radio premiere on the Romanian National Day, at radio ZU, though it premiered on Kiss FM a week earlier.  Elena performed "Midnight Sun" live, on December 31, during a New Year special show, held by Pro TV.  The music video was already shot in Bucharest and it was released via YouTube on May 13, 2011.  The video features many special effects as well as the track listing for Gheorghe's upcoming album.  The song peaked at number-one the Radio Top 50 and charted within the top ten in two other Romanian charts.  In the official Romanian Top 100 it peaked at number-ten, thus making it Elena's fifth song to enter the top ten in Romania, after "Soarele meu", "Vocea ta", "The Balkan Girls" and "Disco Romancing".  The song was performed at many dates throughout Romania. "Come On, James."  is a viral internet meme, internet slang and copypasta in Hong Kong, a quotation born from a fictional satire, "4-Year Curriculum of University", by the famous columnist, Chip Tsao, on the newspaper Apple Daily published in 2004.  It was converted into a number of different versions, including a top trending viral video and a musical parody on YouTube.  It then became an internet slang widely used by Hong Kong netizens. "Come On, James."  now often represents both the satire and the quotation. <br> Ylvis (] ) is a Norwegian comedy duo consisting of brothers Vegard and Bård Ylvisåker.  They debuted as professional variety artists in 2000 and have since appeared in several countries in variety shows, comedy concerts, television shows, radio shows and music videos.  They are currently the hosts of the Norwegian talk show "I kveld med Ylvis" ("Tonight with Ylvis").  Their song and music video "The Fox (What Does the Fox Say?) ", written and filmed for the talk show, went viral on YouTube in September 2013, with over 692 million views as of September 2017 .  They have also released an album called "" that is a mixture of ten singles that they wrote in the past. "Gangnam Style" (Korean: 강남스타일 , ] ) is the 18th K-pop single by the South Korean musician Psy.  The song was released on July 15, 2012, as the lead single of his sixth studio album "Psy 6 (Six Rules), Part 1", and debuted at number one on South Korea's Gaon Chart.  On December 21, 2012, "Gangnam Style" became the first YouTube video to reach one billion and two billion views.  The song's music video has been viewed over 2.9 billion times on YouTube, and was the most viewed video on YouTube from November 24, 2012, when it surpassed the music video for "Baby" by Justin Bieber featuring Ludacris, to July 10, 2017, when it was surpassed by the music video for "See You Again" by Wiz Khalifa featuring Charlie Puth. Brown Rang is a Punjabi language song sung by Yo Yo Honey Singh.  Upon the release the song topped the charts worldwide and captured positive reviews both from the critics and the audience.  The video was released on 28 February 2012 .  it was the biggest hit of the following year and Brown Rang was the YouTube's most trending video of 2012.  It won the top spot in the list of YouTube's most watched video of 2012 in India with over 10 million views.  According to YouTube in Rewind, the song had beaten the popular Korean Song "Gangnam Style" that stood at the second place in the list. The musical rock band OK Go has earned considerable fame for their creative but often low-budget music videos, most of which have been promoted through Internet video sharing sites like YouTube.  Many of these have become viral videos; the 2006 video for "Here It Goes Again", in which the band performed a complex routine with the aid of motorized treadmills, has received over 50 million views four years later.  Their video for Needing/Getting, released February 5, 2012 in partnership with Chevrolet, debuted during Super Bowl XLVI and has over 32 million views on YouTube.  Samuel Bayer, who produced many music videos in the 1990s, asserted that OK Go's promotion of music videos on the Internet was akin to Nirvana's ushering in the grunge movement.  Many of the videos also use long or single-shot takes, which "Salon"' s Matt Zoller Seitz says "restore[s] a sense of wonder to the musical number by letting the performers' humanity shine through and allowing them to do their thing with a minimum of filmmaking interference".  The success of OK Go's music first won the band the 14th Annual Webby Special Achievement Award for Film and Video Artist of the Year.  The video for "This Too Shall Pass" was named both "Video of the Year" and "Best Rock Video" at the 3rd annual UK Music Video Awards. "This Too Shall Pass" won the LA Film Fest's Audience Award for Best Music Video, UK MVA Awards – Music Video of the Year Winner 2010, among others. Play ( ) is the thirteenth studio album by Taiwanese singer Jolin Tsai ( ).  It was released on November 15, 2014, by Warner Music Taiwan.  The album melds dancehall with bubblegum pop, breathtaking love songs with hilariously catty weirdness and euphorically catchy melodies with propulsive rhythms.  The album garnered critical acclaim and was declared as "easily the best album of the year".  The music video of the title track, "Play", became the most-viewed Chinese-language music video of 2014 on YouTube and thrust her into the international spotlight.  Nolan Feeney from "Time" magazine claimed the music video "the year's best pop music video."  The album has sold more than 85,000 copies in Taiwan alone, and made her the best-selling female singer of the year in Taiwan.  The title track, "Play", reached number 1 on the Hit FM Top 100 Singles of the Year.  The ninth track, "The Third Person and I", reached number 8 on the chart.  The album earned Tsai six Golden Melody Award nominations for Best Mandarin Album, Song of the Year, Best Vocal Recording Album, and three Best Music Videos, and she finally won for Best Mandarin Album and Best Vocal Recording Album.  The album also earned Tsai an MTV Europe Music Award nomination for Best Taiwanese Act.  The album also earned Tsai an Mnet Asian Music Award for Best Asian Artist. "a capella" is a song and music video by the Norwegian duo Ylvis.  It parodies a cappella groups like Pentatonix.  Ylvis revealed "a capella" on "I kveld med YLVIS" on TVNorge on January 5, 2016.  Three days after the song's release, it had 250,000 views. "Crystallize" is a song by American violinist Lindsey Stirling from her self-titled studio album, "Lindsey Stirling".  The song was released as a music video on YouTube on February 23, 2012.  The video proved to be a success, with more than 42 million views at the end of the year, and was the eighth-most watched video of 2012.  The song became Lindsey Stirling's album's lead single due to its success.  The song appeared on three "Billboard" charts and, according to Nielsen SoundScan, by April 2013 it had reached 234,000 digital sales.  On February 4, 2014, almost two years after the release of the video, "Crystallize" earned Stirling's first RIAA certified gold record by selling 500,000 copies in the United States.  At the end of 2013, on the year-end chart, "Crystallize" finished first in the chart of Classical Digital Songs.  On July 27, 2014, the official music video reached 100 million views, being Stirling's first YouTube video in doing so.
Answer: 2013