If Bono, U2's lead singer, is the driver of the machine, Adam Clayton, Larry Mullen jnr and Edge are the wheels that make it go round. If the driver is under the weather, his foot easing off the pedal, the machine travels slower.
U2's first date at Slane Castle on Saturday had all the makings of a brilliant, beautiful day: the homecoming to Co Meath 20 years to the month they last played there as support to Thin Lizzy, the inherent symmetry of such an event celebrated with a snippet of Dancing In The Moonlight, and last, but by no means least, the unbearable poignancy (for anyone with a heart, that is) of Bono's father passing away only days before the concert.
The ingredients were there, then, for an unforgettable experience. Yet, having seen U2 previously on the Elevation tour, I found there was something missing at Slane. Allowing, as we must, for extenuating circumstances, Bono, in particular, seemed to lack energy, as if he was flying on one wing only.
The inspiring aspect of the concert was how the 80,000plus audience lifted his other wing, willing him to perform, making him soar, possibly against his better judgment.
The concert started, as all Elevation shows have done, with a cracking pair of songs Elevation and Beautiful Day. End Of The World and New Year's Day followed, but it was song number five, Kite, which provided the first genuine high point of the day. As in previous shows over the past few weeks, Bono dedicated it to his father and, as he sang what is easily one of the best songs he has ever written - a narrative of doubt, change, affirmation in the uncertainty and fragility of life - only the walls of Slane Castle appeared unmoved.
As darkness set in, so did the limitations of the stage show as envisioned for an event of this magnitude. Construed initially as an indoor production - where the subtle use of monochrome, slender banked lights and a few primary colours works wonders - the Elevation show at Slane largely failed to engage the visual senses.
Only at the beginning of Where The Streets Have No Name did it genuinely connect, producing a wow moment that robustly gobsmacked the crowd.
Discarding the synapseblitz of both the Zooropa and PopMart tours, the lack of spectacle, however, was perfectly balanced by the songs - a 20-year back catalogue, the potent power of which still surprises.
If this was a tour that needed to reflect U2 as a bona fide rock band, rather than as musical props surrounded by expensive bells'n'-whistles technology, then it succeeded in no small degree.
This coming Saturday will see U2 driver Bono hopefully more refreshed, less drained of joy.
My guess is that this second concert will be the pedal-to-the-metal one, and not one of palpable restraint.
Can't wait, to be honest.
