The length of its strings distinguishes a grand piano. The longer strings produce a richer sound 
with lower inharmonicity, giving the listener a full, mellow listening experience. I’ve never met a pianist who doesn’t sit down at a grand piano with the expectation of pleasure, knowing what will come from those keys.
An upright grand is a special type of upright piano with a higher back to accommodate the longer strings. These pianos retain the full tones of a grand, but are more easily placed in a smaller home or studio. Tuning an upright grand requires understanding that the longer strings need to be tuned according to grand piano standards, not upright piano standards.
What’s the difference?
The difference is in the overtones, or the inharmonicity. It’s not a simple matter of tuning the strings to the correct pitch; instead, the overtones of the strings need to blend with one another. The longer strings of the upright grand need to be tuned to a lower octave’s overtones so that when two notes in different octaves are struck, the overtones of the notes will blend. This helps to produce the rich, full sound that comes from a grand.
If you hear an upright grand that has been tuned as if it were a standard upright, you immediately notice the difference, although it may be difficult to define. An in-tune, yet improperly tuned, upright grand sounds technically correct but distinctly unsatisfying.
Who should tune it?
A professional. Unless you have been trained to tune a grand piano, you will not be able to keep your upright grand piano sounding full and rich. Tuning a piano is more than making an individual string sound correct; rather, it is understanding that the instrument as a whole has a voice, and each string contributes to that voice. Take the time to find a professional who understands the difference between an upright and an upright grand piano. Talk to people in your area to get recommendations and ask about the tuners experience with grand, baby grand and upright grands as well as standard uprights and other types of pianos. This is your listening experience; you deserve to have everything done correctly.
When should you tune?
Rather than wait until the instrument sounds bad, set up a schedule to have your upright grand piano tuned regularly. Twice a year is recommended, but pianos that are in variable humidity or exposed to rapid temperature changes should be seen to more frequently. Consider a closet door that sticks when it rains. If the shape and size of the door changes that much, think what the humidity is doing to the wood, and consequently the tuning, of your piano. You can minimize these effects by keeping your upright grand away from doors, windows, heat sources and direct sunlight.
Of course, any time the instrument sounds “off”, has been moved, or experiences some failure, a tuner should be called to make sure everything is in working order.
The upright grand piano has a sound all its own that is distinct from that of standard grands and uprights. If you love the instrument, or even if you hate it, tell me why. Does your music lend itself to one type of piano over another? Do you find jazz, for example, just works better on an upright? Tell me your experiences, and why you choose the type of piano you do.