The University Community Chorus and The University of Arizona Philharmonic Orchestra will join forces November 6 and 8 presenting "Town and Gown,” a concert featuring the works of Schubert, Mozart, and Dvořák. The University Community Chorus is under the direction of Dr. Elizabeth Schauer, and the UA Philharmonic by Prof. Charles Bontrager.   The performance will open with Schubert’s Overture, D. 591, Op. 170 in C Major, conducted by Keitaro Harada, one of two inaugural fellows of the James E. Rogers Institute for Orchestral and Opera Conducting.   Following this, conductor Elizabeth Schauer will lead both ensembles in Mozart’s "Thamos, King of Egypt" K345, a historical drama. Although the play that Mozart wrote this music for was not successful, the choruses are energetic and delightful depictions of Thamos’ people worshiping the Sun God. The soloists include Tucson soprano Betty Allen and UA graduate students Heather Zosel, mezzo-soprano; Dennis Tamblyn, tenor; and Greg Guenther, bass.   After intermission, conductor Charles Bontrager will take the podium for Dvořák’s "Te Deum" Op. 103. Both joyful and praiseful, this work contains beautiful solo passages, sung by Betty Allen, soprano; and UA faculty member Charles Roe, baritone. The chorus is prepared by assistant conductor to the University Community Chorus, Heather Zosel.   The concert will be held in Crowder Hall on the UA campus. Tickets are general admission (621-1162).