I will appreciate who can acknowledge me about the differences of chords on an acoustic guitar's fret board with that of a 4-string Bass guitar. how could we perform one's chord on another's and how is it possible to harmonize them?
The standard tuning of the bass strings are the same as the bottom four of standard guitar tuning - E, A, D, G - but one octave lower. The tones of chords are the same between the instruments except they sound one octave lower on bass. So
A2 E3 A3 C#4 on guitar will sound
A1 E2 A2 C#3 on bass guitar, and the fretting can be the same.
In terms of how to perform and "harmonize" them, a typical way that guitar an bass work together is for the guitar to strum the full chord while the bass plays single notes. If the guitar strums an
A chord, the bass may play single tones
E - the root and fifth of the chord - or it could arpeggiate the chord in single tones like
A C# E C#.
One reason the bass plays single notes is because in the lower register playing simultaneous tones sounds "muddy". If you play higher - somewhere around the seven fret on the top three strings - the combined tones become clearer. A lot depends on exactly what is being played.
Rhythmically the bass and guitar parts can differ. If the bass plays straight quarter notes the guitar might strum with some upbeat rhythms. But a whole range of two part playing can be used from playing the exact same part in octaves to completely independent parts.
Bassically, the bass guitar wasn't designed or expected to have chords played on it. The notes are low, and even playing a simple triad often doesn't sound good. Muddy describes it well.
So, using a guitar and a bass, it's best to stick to one note on the bass, and the chord, or the rest of it, on the guitar. Thus, the bass could play one of the triad notes - usually 1, 3 or 5, with 1 being the best as it's the root note.
If you really want to play chords on a bass guitar, then it's possible. For instance, playing the root on bottom string, appropriate fret, and 3rd on the top string, one fret higher (for a major chord), or 3rd on same fret (for a minor chord). Only a two noter, but it sounds fine.If you wanted to put the 5th in, it could go on the A string, two frets higher than the root note's position.
As David states, the bottom 4 strings on guitar are tuned as the bass is, so any notes fingered as on those 4 strings on a guitar can be fingered the same on bass, with the understanding that the lower frets on bass tend to be bigger, and the sound will not usually be good.
As stated above, playing riffs of single notes on the bass is the primary use of the instrument (either finger-style or picked). Certainly that has been my experience having played the bass guitar in gigging bands for about 35 years. "Chords" are possible high on the neck. I use the term loosely on 2-note chords above the octave or riffs of notes that are plucks and left to sustain into a "chord" for a few beats. I'm thinking of the bass intro to Steely Dan's "Peg" for the high neck 2-note "chords" or the intro to Aerosmith's "Sweet Emotion" for the high-neck riff of notes that is left to sustain a bit.
But adding to the comments above with regard to the harmonizing question, I would also mention the style of music being played would also contribute to harmonizing the bass with guitar. If we look at a guitar chord like an A-major which is A-C#-E, I think of that as a 1-3-5 chord (the whole major octave being 1-2-3-4-5-6-7-8). A being the 1, C# being the 3 and so on. So for a country tune, I might bounce back and forth in time between the 1 and 5. For a 12-bar blues, a "walking bass" might be appropriate that traverses chromatically up and down a 1-3-5-6-7b (possibly like "Pride and Joy" by Stevie Ray Vaughan). For a dance or disco type tune, an octave bounce between the 1 and 8 is common, even doubling up over the primary guitar or keyboard riff like "Disco Inferno" by the Trammps. Ballads typically call for single notes that are designed to directly harmonize and enhance the treble instrument. I'm thinking of "Color My World" by Chicago. An excellent application of harmonization as an enhancement between the bass and the piano leaving the pianist free of having to even touch the bottom half of the keyboard. Hope this helps.