For those uninitiated...
The great-grand pa of our beloved electric slabs, was the Viola da Gamba (family). They actually had moveable frets. You see that with the Sitar.
The Double Bass (i.e., Upright, Stand Up, Dog House, etc), was the next descendent, although this is not a 100% consensus. The frets were removed. Early Double Basses had only 3 strings.
Then, some whacky dudes (i.e., Tutmarc, Fender, others) reintroduced the frets, along with pickups, amplifiers, and speakers (this is a hundred years of development compressed into a single sentence - enough with the Leo Fender stuff, he was NOT the first).
As far as "how to tune your bass," observe violinists. They start with a reference "A", from either an Oboe (if playing with an orchestra), or Piano (if playing with a pianist). They then tune the open A-string to the reference, followed by tuning the open D-string to the open A-string, then the open G-string to the open D-string. At this point the G-string will NOT be in tune with the G from the Piano. They will often ask for a G, from the Piano, and make the slight adjustment (especially if the piece to be performed is in "G" and/or requires a lot of open G-string playing, of which there can be no adjustments made during the performance - vibrato, slight finger position adjustments. Lastly, they will tune the open E-string to the open A-string.
If the violinist tunes with the open string method only, the G-string will be 4 cents flatter than the G from the piano.
This phenomenon will occur, if you tune your bass with harmonics. I often see/hear a bassist first tune the harmonic, above the 7th fret of the D-string (i.e., an "A"), to the "A" from a piano. If they are exactly in tune with each other, the open D-string will now be flat to the Piano. Then they continue the similar method to tune the E-string (becomes even flatter), then tune the G-string by attempting to match the G-string 7th-fret harmonic to the D-string 5th-fret harmonic (which is flat 2 cents). This method now renders a flat open G-string (4 cents flat).
Oy vey! I think I extrapolated this correctly.
The good news, we are talking about a couple cents -- each half-step (i.e., one fret to the next) is divided into 100 equal parts. Think a Penny to a Dollar. Hardly anyone is going to notice a few cents, here or there. And, there is always the Chorus Pedal option - which proves that most people enjoy some "out-of-tuness".
