String Ensemble,String Trio Cello,Violin - Level 3 - Digital Download SKU: A0.1497034 Composed by Giacomo Puccini. Arranged by Homco/Crinion. Opera,Romantic Period. 8 pages. Homco/Crinion #1073450. Published by Homco/Crinion (A0.1497034). Un Bel Di (One Fine Day) is a soprano aria from Giacomo Puccini's opera Madame Butterfly. It is the most famous aria in the opera, and in fact, is one of the most popular pieces in the entire repertoire for sopranos. It is a very emotive melody that encapsulates the tragedy that is at the heart of the opera. This arrangement gives each instrument a chance to voice that heart-wrenching melody.