In watchmaking, a complication is any mechanical function added to the simple indication of hours and minutes. Not all complications carry the same technical weight: there is a sidereal distance between a moonphase and a minute repeater, even though both bear the same name.
Acoustic complications are historically the most demanding. The minute repeater activates hammers that strike gongs or bells to mark hours, quarters, and minutes on demand — traditionally via a side lever. The challenge is not merely mechanical: it is acoustic. Achieving a clean, projected sound within a confined case requires years of refinement. The Grande Sonnerie sounds hours and quarters at every time interval; the Petite Sonnerie sounds only the full hours. Both belong to that tier where few maisons still possess the expertise to enter.
Astronomical complications range from the perpetual calendar — which autonomously compensates for short months and leap years until 2100 — to the tellurium, which reproduces the relative positions of Earth, Sun, and Moon in orbit. The annual calendar requires only one manual intervention per year, on January 1st: it is less complex than the perpetual, but far more practical than the simple calendar. The Equation of Time adds a fourth central hand that indicates true solar time, different from calendar mean time by a variable amount each day of the year.
Display complications have their own logic. Jumping hours accumulate energy and release it all at once to advance the hour disc instantaneously, without transition. A demanding mechanism: any bounce onto the next numeral is unacceptable. Retrograde minutes use an arc hand that, upon reaching the end of the scale, snaps sharply back to the beginning. True GMT maintains an independent hour hand for the second time zone, without touching the main movement.
There exists, then, a philosophy I might call hidden complications: functions that disappear from the dial when not activated, maintaining readability under normal conditions. The tourbillon, finally, compensates for gravity's effects on the oscillator: born for pocket watches in fixed vertical position, on a wristwatch in continuous motion its practical benefit is debated, yet its constructive complexity remains real.
At the bench I learned one thing: the number of complications on a watch says little. What matters is how they are integrated, how they dialogue with one another without robbing space from the barrel.