pipes, and a bellows were missing. For this reconstruction all the surviving elements were used and, on the basis of these, also making comparisons with the organ of San Giovanni Evangelista, the measures of the pipes were established. The restoration made it possible to appreciate again the round and robust sounds of the Callido organ and the transparent and delicate timbre of the Piaggia organ, closer to Renaissance sound models. Eventually, the instruments were tuned in unison, in order to be played together. After more than thirty years, a new revision work was promoted, which was completed in the months of April and May 2004. Thanks to the availability of two organs placed on two opposing choirs that was typical of a musical style in vogue in Venice in the sixteenth and seventeenth centuries, the practice of the double choir is restored in the basilica of the Frari. It is the last surviving example in Venice - and one of the rare examples in Italy - of two choirs with functioning historical organs. Piaggia organ The organ of the left choir was built by Giovan Battista Piaggia. It features an original integral mechanical transmission, has a single keyboard of 45 notes with a first octave scavezza (C1-C5), and a pedalboard of 13 (C1-E2) with a first octave scavezza, constantly combined with the manual. The exhibition consists of 21 pipes, belonging to the main register and forming a single cusp with side wings and with aligned shield mouths. The phonic arrangement, based on the position of the knob tie rods of the various stops in a column of the register (whose handwritten tags are original), is as follows: Main 8 ' Octave Tenth Fifth Tenth Ninth Second Vigesima Vigesima Sixth Vigesima Nona Human Voice Twelfth flute Handset Double basses 16 '(always inserted) Callido organ The organ of the right choir is the pipe organ built by Gaetano Callido. It has an original integral mechanical transmission. It has a single 47-note keyboard with first octave scavezza (C1-D5) and a 17 + 1 pedalboard (C1-G # 2 + Rollante pedal) with first octave scavezza, constantly combined with the manual. The exhibition consists of 21 pipes, belonging to the main register and forming a single cusp with lateral wings and with aligned miter mouths, at the foot of which the tromboncini are housed. Mascioni organ The basilica also housed the Mascioni opus 398 pipe