The ever popular Yamaha U1. I want to talk about why this piano is sought after, and what makes it so great.
The Yamaha U1 is 48 inches, or 121 centimeters. It's made in Japan, has a solid spruce soundboard and ribs and has been seasoned for the North American Market. Almost everything else about the piano is the same for most pianos. I mention these things because many brands, including Yamaha, make pianos with plywood soundboards, and other brands use only one seasoning process. Yamaha seasons their instruments for 3 zones, "wet," "dry," and "superdry." The homes in North America are in both wet and dry climates, but since we use central heating and our winters are cold and dry, even the tropical regions dry out. So Yamaha alter's the building process slightly for these pianos and calls them "superdry." For example, the U1 has super tight tuning pins. The idea is that when the piano goes through year after year of fluctuations in humidity, the tuning pins will remain tight. This is pretty much the most important example to provide you with. Others are how much they dry out the wood for the soundboard and ribs, key bed, etc. Tuning stability reins over all. If you can't tune the instrument, there is no point to anything else.
How about reliability? The Yamaha U1 is a workhorse! It's commonly purchased en-mass by universities and conservatories. Some practice room complexes allow students to practice at any hour of the day or night, so it's common that practice room instruments are played 12 hours a day. The technicians tune each piano every two weeks and make general repairs and scheduled maintenance. Is a U1 unbreakable? No. Even you may get a nail or screw in your tire every 100,000 miles. Sometimes things unexpectedly break, but, all-in-all, the parts remain consistent, stable, and functional. After all, if a university has over 100 practice room pianos, lots of troublesome work would create a nightmare situation for technicians, not to mention for the students and staff.
So, the construction is insanely consistent for a piano, they function well for years on end, what about the tone and voice? I have to say that the tone is bright, and boring. I can articulate very well on a U1, but the voice is almost computerized. Many would say it leaves something to be desired, and I will agree with this. But it brings me to my main point about this instrument. The overwhelming majority of Yamaha U1's end up in conservatories, and it's almost required that practice pianos remain consistent. If a student practices flute, guitar, trombone, double-bass or anything else, (well, maybe not drums) they can take their instrument from one lesson to another, and take it home to practice, or play in the street. A student of the flute becomes better when they practice and perform consistently, and for a while they need the same personal instrument to achieve this. The piano student can not take their piano with them, so they need to be able to practice on what seems like the same instrument in every classroom or practice space. This is why the Yamaha U1 is so good: they produce a high quality instrument that is so consistent and stable so that students won't know the difference when practicing in different rooms.