This piano was more than a half step flat! Tuning something this poorly maintained is not much fun, but the task is made much easier by an ETD (Electronic Tuning Device). If you watch the display carefully, you can see, as well as hear, each of the three strings rise in pitch until they are all at the target pitch.
Customers often ask about the difference between tuning by ear (aurally) vs. using an electronic device. Some people hold to strong positions one way or the other. At the end of the day, the quality of the tuning is what matters! I use both methods, but I tend toward mostly aural for fine tuning quality instruments, and mostly electronic for a first-pass pitch raise like this, where all you can expect is to get it in the ballpark.