In order to to satisfy the audience the musicians have to play in a certain order, which is:
Piano, Tuba, Piano, Tuba, Sax, Piano, Violin, 3×Guitar, Shotgun, Trumpet, 3×Tuba
You will receive a "Bravo!" and $130

First you need to get into the orchestra hall:
Get rid of the cat at the entrance: give "Valerian Root" to cat
Next there is Mr. Fartini. He wants:
× Rosin (at #91 Radio station)
× Violin (in Antique Shop in exchange for a mummy)
× Beethoven's sheet music (in teepee #86 in exchange for pipe from the avid reader/smoker #40)
× Phonograph (in Antique shop in exchange for Samovar...)