An analog strobe tuner like a Peterson 490, Peterson 450, Peterson 420 or a Conn ST11 all use a rotating strobe disk and light flashing at the frequency of the pitch you are playing to show you what you are hearing. You can see more than one note at a time and you get to see how they are, relative to each other.
You are tuning sound at the speed of light. That's something no other tuner - even the so-called digital strobe tuners can't do. They work at about an interval of 100 milliseconds. That's why the needle or any other form of display is so choppy.
Here, I'm tuning a blow reed plate in the key of C. Every note of the blow plate is part of the major triad - so each note has very strong potential for harmony. And any instrument with strong harmonies can fill the room with sound. Little instrument, big sound.
We tune notes relative to one another. Tuning notes as single entities is a waste of time. We make the pitch go up and down as we play by changing our breath and tensing our muscles. When you play two notes at the same time, you eliminate those errors because both notes are subject to the exact same influence. So it cancels itself out.
We tune the octave first - 4 and 7 blow.
Then we tune the fifth -7 and 6 blow
Then the third - 4 and 5 blow
If we do things right, the 5 and 6 blow will be in tune. This is a good way to verify your work and "square things off" just like in carpentry.