Question: What is the name of the bassist, one of the founding members of the Seattle based American Rock band Soundgarden, who left the band in 1989 and started an independent rock band Truly together?
Context: Truly is an American rock band formed in the wake of the grunge era.  It featured singer-guitarist Robert Roth, bassist Hiro Yamamoto, and drummer Mark Pickerel.  Yamamoto and Pickerel were founding members respectively of Soundgarden and Screaming Trees.  While not a commercially successful group like some of their Seattle contemporaries, the band lasted a decade with two studio albums to their name. Chris Cornell was an American rock musician from Seattle, Washington.  He began his career in 1984 when he formed grunge band Soundgarden with guitarist Kim Thayil and bassist Hiro Yamamoto, originally playing drums in addition to vocals before Scott Sundquist took over the former the following year.  The group contributed three songs to the C/Z Records compilation "Deep Six" in 1986, before Sundquist was replaced by Matt Cameron.  After two extended plays (EPs), Soundgarden released its debut full-length album "Ultramega OK" in 1988, on which Cornell was credited for songwriting on all but one of the eleven original songs. " Louder Than Love" followed in 1989, on which Cornell was credited solely for writing seven of the album's twelve songs (and co-credited on four of the other five). Hiro Yamamoto (山本 紘 , Yamamoto Hiro , born April 13, 1961) is an American bassist who was a founding member of grunge band Soundgarden, along with Kim Thayil and Chris Cornell in 1984.  He left the band in 1989, and two years later, he started the independent rock band Truly together with Screaming Trees drummer Mark Pickerel and Robert Roth from The Storybook Krooks. Down on the Upside is the fifth studio album by the American rock band Soundgarden, released on May 21, 1996, through A&M Records.  It is the band's third album with bassist Ben Shepherd.  Following a worldwide tour in support of its previous album, "Superunknown" (1994), Soundgarden commenced work on a new album.  Self-produced by the band, the music on the album was notably less heavy than the group's preceding albums and featured the band experimenting with other sounds. "Black Rain" is a single by the American rock band Soundgarden, featuring lyrics written by frontman Chris Cornell and music written by bassist Ben Shepherd and guitarist Kim Thayil.  The single debuted at number 24 and number 14 on the US "Billboard" Alternative Songs chart and the US "Billboard" Rock Songs chart respectively in August 2010.  It is also Soundgarden's first and currently only song to chart on the "Billboard" Hot 100, peaking at #96.  The song appears on the compilation album "Telephantasm" and on the music video game "" and "Guitar Hero Live".  It was the first single that Soundgarden had released since 1997. Ultramega OK is the debut studio album by American rock band Soundgarden.  It was released on October 31, 1988 in the United States and in January 1989 in the United Kingdom through SST Records.  Following the release of the EPs "Screaming Life" (1987), and "Fopp" (1988), both for the Sub Pop record label, Soundgarden signed with the independent record label SST and went to work on its first full-length studio album.  The resulting album contained elements of heavy metal, psychedelic rock and hardcore punk. Soundgarden is an American rock band formed in Seattle, Washington, in 1984 by singer and rhythm guitarist Chris Cornell, lead guitarist Kim Thayil, and bassist Hiro Yamamoto.  Matt Cameron became the band's full-time drummer in 1986, while bassist Ben Shepherd became a permanent replacement for Yamamoto in 1990.  The band dissolved in 1997 and reformed in 2010.  Cornell remained in Soundgarden until his death in May 2017, putting the band's future in doubt and leaving Thayil as the only remaining original member of the band. Secret Cities is an independent rock band from North Dakota.  Its founding members, Charles Gokey and Marie J. Parker, met at a band camp in July 2001, while in high school.  Although the two lived 500 km apart, in Fargo, North Dakota and Williston, North Dakota, respectively, the two started making music by exchanging tapes in the mail and composing using four-track recorders.  They continued in this fashion until February 2004, when the pair changed their name to The Foliage and put out their first release on Fall Records, a split with In Ink Please entitled "How to Make Better Love."  In July 2005 the band released a mini-LP, "Zurich" on Fall Records under the moniker The White Foliage.  The group also added a third member, Alex Abnos, during a tour of the Midwest in that year. "Bleed Together" is a song by the American rock band Soundgarden.  Written by frontman Chris Cornell, "Bleed Together" was first released in the United States on Soundgarden's post-breakup greatest hits album, "A-Sides" (1997).  It had previously appeared as a B-side on some foreign copies of the band's 1996 single, "Burden in My Hand".  It was released as a single in November 1997 in support of "A-Sides", and was the first single released by Soundgarden, after the band's breakup in April 1997.  The song peaked at number 13 on the "Billboard" Mainstream Rock Tracks chart. "Spoonman" is a song by American rock band Soundgarden.  Written by former frontman Chris Cornell, "Spoonman" was released on February 15, 1994 as the first single from the band's fourth studio album, "Superunknown" (1994).  "Spoonman" is often credited as one of the songs that launched Soundgarden's career into the mainstream.  The song peaked at number three on the "Billboard" Mainstream Rock Tracks chart and number nine on the Modern Rock Tracks chart.  A remixed version of the song by Steve Fisk appears on the "Black Hole Sun" and "My Wave" singles.  The song was included on Soundgarden's 1997 greatest hits album, "A-Sides" and the 2010 compilation album "Telephantasm".
Answer: Hiro Yamamoto