Mozart, on the other hand, was definitely overstepping the bounds of opera seria, taking full advantage of the Mannheim resources at his disposal (as was emphasized in the book Mozart: The Early Years 1756–1781 by Stanley Sadie and Neal Zaslaw). This was not just a matter of exploiting "Mannheim dynamics" for the sake of dramatic impact. It also involved using the orchestra to greater advantage than was usually the case in opera at that time. Most important were his efforts towards a seamless flow of the action, resulting in arias whose conclusions would then immediately launch the next phase of the action. That seamlessness was further reinforced by having the recitativo passages accompanied by the full orchestra, rather than a keyboard-based continuo. This was a technique that Christoph Willibald Gluck had engaged with powerful effect in his Iphigénie en Tauride, which predated Idomeneo by about two years. Mozart was well aware of Gluck's innovative departures from the opera seria traditions of the time; and his "inner twenty-year-old" was probably champing at the bit to show off how he could strut the same stuff and take it to the next level.
When we move from the orchestra pit to the stage, we see that Mozart is also showing off what he could do with his resources. Most striking is probably the extent to which he uses multiple voices to greatest dramatic effect. Thus, the only duets we hear are embedded in choral passages and are sung by secondary characters: two Cretan women praising Idamante and two Trojan prisoners celebrating their liberation. (Could that latter pair have been an inspiration when Ludwig van Beethoven was working on Fidelio? The prisoner duet is there even as early as the 1805 Leonore version.) The first time the major characters sing together is in the second act terzetto for Idamante, Elettra, and Idomeneo, just before the former two are to board the ship that will take them for Argos, as Idomeneo has commanded. By this time we have a full grasp of just how conflicted the emotions of these three characters are, and Mozart's pen was stoked to let those conflicts weave through a counterpoint that displaced the usual dialog between soloist and orchestra. After the resulting catastrophe thwarts Idomeneo's wishes, we are back on "aria turf" until those conflicted characters come together again, this time in a quartet with Ilia added to the mix. This is dramatic emphasis at its best, and it allows us to appreciate that Mozart could be as good with subtlety as he could be with show-off display.
All of these skills were exhibited in the best possible light in yesterday afternoon's San Francisco Opera performance. Conductor Donald Runnicles has always had an excellent sense of how to pace Mozart, so the flow of the music was flawlessly delivered to support the flow of the drama. However, for those interested in whether or not the uncontrollable fates always have the upper hand over free will, we need to consider the case of the part of Idamante. For reasons that I shall not try to understand (let alone explain), the San Francisco Chronicle decided to give "full-court press" (pun intended) publicity to the return of Alice Coote to San Francisco to sing this role. This effort then begat a review that came a bit too close to suggesting that Coote was the only reason for seeing this product. Could this review have provoked the fates into visiting Coote with a back injury? The scenario of Idomeneo would certainly encourage us to ask that question, but the more important question was how prepared the San Francisco Opera was to go this particular distance without her. It turns out that she was replaced by first-year Adler Fellow Daniela Mack, who had just made her San Francisco Opera debut as one of the raunchy members of Marietta's theater troupe in Die Tote Stadt. This may not have been a "star is born" occasion (since Mack already has a rather impressive resume); but she definitely did not disappoint. There were a few awkward moments with the staging, and the astute ear could hear the way she was finding her voice in her first aria. However, she was on solid ground by the end of that aria and remained there for the rest of the performance. If the fates were trying to humble a public relations push, then Mack's free will trumped those fates as surely as the free will of both Idomeneo and Idamante prevailed over the force of Neptune!