Symphony Orchestra, Michael Tilson Thomas conducting, during their S&M2 concerts at Chase Center, San Francisco on September 6 and 8, 2019. Instrumentation Iron Foundry is scored for piccolo, two flutes, two oboes, English horn, two clarinets, bass clarinet, two bassoons, contrabassoon, four horns, three trumpets, two trombones, bass trombone, and tuba, timpani, snare drum, bass drum, cymbals, tam-tam, iron sheet, and strings. Analysis The piece is written in ternary form. It begins with an allegro section, consisting of brief chromatic figures across the orchestra that build slowly to a trio section, after which it returns to the feeling of the allegro beginning for the coda. In this way Mosolov "coordinates the mechanistic rhythms into specific orchestral groups that work together like cogs in a well-oiled machine." Mosolov uses a live orchestra to create a factory-like sound, unlike Antheil's Ballet mécanique, which uses mechanical elements to reach its musical goals. Introduction The piece begins as a representation of the start of the machine, with a tam-tam stroke and repetitious figures that begin in a few instruments and, measure by measure, are added to the sound until the instruments join together to suggest the sound of a factory at work. By measure twenty-seven, the overlapping instruments create a deliberate and machine-like sound above which the horns are directed to stand and play the main theme of the piece. Trio At the trio, the machine suddenly shuts down. Upper winds and the snare drum push forward to a syncopated exchange between the low brass and upper winds and marked by the bass drum and tam-tam. This gives way to a steady, march-like timpani motif that drives the orchestra back to the atmosphere of the beginning. Coda Now the machine has returned to full power. Musical ideas from the introduction are reintroduced, and the piccolo and iron sheet are added to the texture. Some performances, including those of the Interlochen Arts Academy and Royal Concertgebouw Orchestra, interpret the iron sheet part (see figure) as both for iron sheet and orchestral anvil, with anvil strikes on every beat as indicated by the vertical accents; however, the conductor's score published by Kalmus includes a note that the sheet is to be vibrated at each vertical accent and for the sheet to vibrate naturally between beats. The last ten measures of the piece accelerate and grow louder until the penultimate measure, where most of the instrumentation drops