Question: Big Sir is Juan Alderete's what?

Context paragraphs:
Now That's What I Call Big Sir: Now That's What I Call Big Sir is a remix album by Big Sir.  It consists of various remixes of songs from their first self-titled album.

Big Sir (band): Big Sir is a band that includes the bass guitarist Juan Alderete (The Mars Volta and Racer X) and the singer Lisa Papineau.

Juan Alderete: Juan Alderete de la Peña (born September 5, 1963) is a Mexican-American musician, best known as the longtime bassist of Racer X and The Mars Volta.

Los Sueños de un Hígado: Los Sueños de un Hígado (English: The Dreams of a Liver ) is a live album by Omar Rodriguez Lopez Group which was recorded for the BBC on March 11, 2009 at Maida Vale Studios, England.  The album features Omar Rodríguez-López, Thomas Pridgen, Juan Alderete de la Peña, Marcel Rodriguez-Lopez, Ximena Sariñana and Mark Aanderud and was released digitally via Rodriguez-Lopez Productions on September 27, 2009.  A limited edition of 1,000 vinyl was released on December 1.

El Grupo Nuevo de Omar Rodriguez Lopez: El Grupo Nuevo de Omar Rodriguez Lopez is a band consisting of Omar Rodriguez Lopez (guitar), Cedric Bixler-Zavala (vocals), Juan Alderete de la Peña (bass guitar), Jonathan Hischke (synth bass) and Zach Hill (drums).

Big Sir (album): Big Sir is the first album by Big Sir, which is composed of bassist Juan Alderete and vocalist Lisa Papineau.

Zavalaz: Zavalaz is an American rock band from Los Angeles, California, formed in 2013.  It features singer/guitarist Cedric Bixler-Zavala, guitarist Dan Elkan, bassist Juan Alderete and drummer Gregory Rogove.

Racer X (band): Racer X is an American heavy metal band formed in 1984 in Los Angeles, California.  The group has gone through a hiatus, and a few lineup changes with founders vocalist Jeff Martin and bassist Juan Alderete being the sole constant members.  The band is signed to Shrapnel Records.

Cizaña de los Amores: Cizaña de los Amores is the seventeenth studio album by Omar Rodríguez-López as a solo artist.  It was released on October 18, 2010 on CD and vinyl by Rodriguez Lopez Productions on Koncurrent in Europe, then November 18 through the US hello merchandise store.  It is the first collaboration between Omar and vocalist Lisa Papineau, who had previously worked with The Mars Volta bandmate Juan Alderete in their band Big Sir.  This record features the song "Victimas del Cielo" in studio form, having first been released on the live album "Los Sueños de un Hígado".

Und Die Scheiße Ändert Sich Immer: Und Die Scheiße Ändert Sich Immer (German for "And the Shit Is Always Changing") is the second album by Big Sir, which includes The Mars Volta bassist, Juan Alderete, and Lisa Papineau of Air and M83.

Supporting paragraphs: Big Sir (album) Juan Alderete
Answer: first album