Question: The writer of the lyrics for the musical "Rex" collaborated with what composer on "Fiddler on the Roof"?

Context paragraphs:
Jerry Bock: Jerrold Lewis "Jerry" Bock (November 23, 1928November 3, 2010) was an American musical theater composer.  He received the Tony Award for Best Musical and the Pulitzer Prize for Drama with Sheldon Harnick for their 1959 musical "Fiorello! " and the Tony Award for Best Composer and Lyricist for the 1964 musical "Fiddler on the Roof" with Sheldon Harnick.

Randal Bays: Randal Bays (born 1950) is a fiddler, guitarist and composer.  The American-born Irish-style fiddle and guitar player first gained international recognition through his recordings and performances with Co.  Clare fiddler Martin Hayes in the early 1990s.  He began playing music at the age of eight and was widely known as a fiddler in the U.S. long before recording with Hayes as guitar accompanist.  Born in Indiana in 1950, Bays relocated to the Pacific Northwest as a teenager and has made his home in Oregon and Washington since then.  His musical life included serious study of the classical guitar, prior to taking up Irish fiddling in the 1970s.  At the time, he lived in Portland, Oregon, and was strongly influenced by Co.  Cavan accordion player Michael Beglan, also fiddler Kevin Burke and guitarist Mícheál Ó Domhnaill.

Dennis Courtney: Denis Beaulne (born April 30, 1958), better known by his stage name Dennis Courtney, is an American stage director, choreographer, actor and teacher of master classes in auditioning for the theatre.  As a director, he is notable for winning the 2008 Israeli National Theatre Prize (Israel's TONY Award equivalent) for his work in the Cameri Theatre production of Fiddler On The Roof, in Tel Aviv.  The production closed on January 27, 2016 after a near 8-year run.  As an actor, he made his Broadway debut in the 1979 production of Peter Pan with Sandy Duncan and George Rose.  Subsequent Broadway/National Tour/Production credits include Shenandoah with John Raitt (1984), Joseph And The Amazing Technicolor Dreamcoat (1984), Roza (1987) and Starlight Express (1989-1990).  He directed and choreographed a production of My Way, for the Riverside Center Theatre in Virginia and It Shoulda Been You starring Kim Zimmer and for Gretna Theatre in July and August 2016.  In early 2017, he directed and choreographed Kiss Me, Kate at Kent State.  In March 2017 he directed the pre-Broadway workshop production of The Last Adam, a new musical by George Alex Livings and Jonathan Hickey.  He has collaborated with playwright David Brian Colbert on a new play with music about the life of legendary performer, Ethel Waters, entitled .  The play is currently in development.

Fiddler on the Roof (film): Fiddler on the Roof is a 1971 American musical comedy-drama film produced and directed by Norman Jewison.  It is an adaptation of the 1964 Broadway musical of the same name, with music composed by Jerry Bock, lyrics by Sheldon Harnick, and screenplay by Joseph Stein.  Starring Topol, Norma Crane, Leonard Frey, Molly Picon, and Paul Mann, the film centers on Tevye, the father of five daughters, and his attempts to maintain his Jewish religious and cultural traditions as outside influences encroach upon the family's lives.  He must cope both with the strong-willed actions of his three older daughters, who wish to marry for love – each one's choice of a husband moves further away from the customs of his faith – and with the edict of the Tsar that evicts the Jews from the town of Anatevka.  Throughout the film, Tevye breaks the fourth wall by talking directly to the audience as well as to God.  In addition to the difficulties of being poor, Tevye speaks of the Jewish community's constant fear of harassment from their non-Jewish neighbors.

A Shoggoth on the Roof: A Shoggoth on the Roof is a parody musical of "Fiddler on the Roof" based on the works of H. P. Lovecraft.  Published by the H. P. Lovecraft Historical Society, it is credited to a member of the society who is referred to only as "He Who (for legal reasons) Must Not Be Named".

Green Violinist: "Green Violinist" is a 1923-24 painting by artist Marc Chagall that is now in the permanent collection of the Solomon R. Guggenheim Museum in New York City.  The work depicts a fiddler as the central figure who appears to be floating or dancing above the much smaller rooftops of the misty gray village below.  This work is often considered to be the inspiration for the title of the 1964 musical Fiddler on the Roof.

Rex (musical): Rex is a musical with music by Richard Rodgers, lyrics by Sheldon Harnick and libretto by Sherman Yellen, based on the life of King Henry VIII.  The original production starred Nicol Williamson.

Cannonball Adderley's Fiddler on the Roof: Cannonball Adderley's Fiddler on the Roof is an album by jazz saxophonist Cannonball Adderley released on the Capitol label featuring performances of material from the Broadway musical "Fiddler on the Roof" by Adderley with Nat Adderley, Charles Lloyd, Joe Zawinul, Sam Jones and Louis Hayes.

Sheldon Harnick: Sheldon Harnick (born April 30, 1924) is an American lyricist best known for his collaborations with composer Jerry Bock on musicals such as "Fiddler on the Roof".

Alexandra Silber: Alexandra Michelle Silber (born July 3, 1983) is an American actress, singer, writer and educator.  She has performed roles on Broadway, in London's West End, on television and film, and concert stages.  Among other stage roles, in London, she created the role of Laura Fairlie in "The Woman in White" (2005), played Hodel in "Fiddler on the Roof" (2007) and Julie Jordan in "Carousel" (2008).  In New York, she appeared in "Hello Again" (2010), "Master Class" (2011), created the role of Sara Jane in "Arlington" (2012–14) and as Tzeitel in the Broadway revival of "Fiddler on the Roof" (2015).

Supporting paragraphs: Rex (musical) Sheldon Harnick
Answer: Jerry Bock