The Anatomy of the Tongue in Cheek in 2001. Since the release of Mmhmm in 2004, his piano playing started becoming more prominent, and he began including a piano onstage as well. Solo projects and collaborations In addition to being in Relient K, Thiessen plays in his own solo piano project called Matthew Thiessen and the Earthquakes. Prior to 2018, the project had released a total of five songs on various samplers and compilation albums from Gotee and Mono Vs. Stereo, and several songs written for the project have been re-recorded on Relient K releases. In 2010, after the release and supporting tour of Forget and Not Slow Down, Thiessen announced that he would begin work on a full-length solo album. Although he had previously expressed interest in recording a studio release, he had placed his priority on Relient K, and relegated his solo work to his free time. In April 2018, Adam Young of Owl City announced that Matthew Thiessen and the Earthquakes would be joining them on tour later in the year. In June 2018, Thiessen announced that his debut album under Matthew Thiessen and the Earthquakes, Wind Up Bird, would release later that summer. Thiessen has occasionally collaborated with Jon Foreman of Switchfoot. After initial interest in recording vocals for a Switchfoot song, it instead worked out for Foreman to contribute vocals for the Relient K song "Deathbed" from Five Score and Seven Years Ago. He later contributed songwriting and vocals to the Switchfoot release "Rebuild" in 2007, in conjunction for the Appetite for Construction Tour. In 2009, he contributed vocals, songwriting, and production to Owl City's major-label debut Ocean Eyes, which has sold over 1,500,000 copies worldwide and reached the top ten on the Billboard 200. Lead single "Fireflies" reached number one on the Billboard Hot 100 in late October, and was a global success, topping the charts in many countries including Australia, Denmark, the Netherlands, and the United Kingdom. Thiessen continues to work with Owl City's Adam Young and contributes vocals to "Plant Life", a song on the album, "All Things Bright and Beautiful". He also co-wrote "Good Time" with Owl City and Brian Lee. Thiessen has also made guest contributions on a number of releases with other artists, including Blackbear, John Reuben, tobyMac and The Fold. Musical style and influences Thiessen has received piano lessons since he was seven years old, with early interests