Pierre Petit and the Cuckoo Clock Pendulum

Today we had one of those random conversations that actually proved quite interesting.
It started when Robin asked me to guess how many beats per minute (bpm) the cuckoo clock pendulum was going.
Initially I said 80 bpm but quickly revised that to 110 bpm.
Robin listened intently for a few seconds then estimated it at 140 bpm.
He got one of his metronomes and 'tapped' along to the pendulum until it informed us that the rate was actually 139 beats per minute.
I was pretty impressed that Robin had been so close with his guess and he profered an explanation.
Toccata by Piere Petit is a fabulous piece that Hill/Wiltschinsky have played many times and recorded. They feel that to gain optimum excitement it should be performed at 155 bpm. So in his mind he'd run through a few bars of 'Toccata' and made a mental adjustment to assess the speed of the pendulum.
Why he chose that piece I'm not quite sure as technically he could have achieved the same result with any. At least it shows a good sense of timing which is essential in his job.
Unlike the cuckoo clock which is usually at least 10 minutes early...