Musical instruments are not exempt of the Universal First Law Of Thermodynamics And Conservation Of Energy. *
I will try to keep this simple - but that's asking a lot of me.
Since the wood of a slab guitar isn't active and contains no stored energy it can only attenuate (diminish by absorption) sounds/vibrations and is not therefor additive. {see footnote 1}
If the body absorbs mostly only certain ranges of frequencies or is resonant to one or just a few of them, then the non-absorbed frequencies sound more forcefully to the hearer.
An instrument may be 'resonant' - but is only passively so and in logical orders of magnitude.
Since most people falsely believe that solid wood bodies can add to 'tones' or gloriously amplify certain ranges or frequencies, one can find themselves in a heated debate about wood/woods/wood qualities and other untenable yet glorified and nebulous factors.
If the body then can be caused to vibrate at a certain frequency - where did that energy to excite it come from and at what cost?
Think about it - in the realm of musical instruments - the wood is passive and only subtracts from and cannot add to any sound generation by and of itself.
The wood is dead.
It cannot of or by itself add to anything without the use of some form of outside energy input, ie: you don't get something for nothing.
That energy would only be taken from the plucked/oscillating string.
Energy can neither be created nor destroyed - it can only be converted or changed from one form to a different one.
That is an inviolate truth.
The somewhat limited capacity of the slab body to resonate does however act as an absorptive wooden 'sponge', taking away certain ranges of frequencies according to it's density, moisture content, shape, position of string attachment, contour and thickness, and molecular composition thereof - to only resonate within a narrow range of frequencies.
Finishes, paints, coatings, wax, hardware, bridges and even screws in the body all also act as absorptive devices. These too cannot 'add' to- but only subtract from- the sound emanating from the instrument.
These only serve to alter the subjectively perceived sounds in a diminished capacity since they would require energy to cause them to vibrate (that requires energy to set them in motion - and is one of the universal physical laws of energy conservation) - and they too will decrease or eliminate the sound quantity or quality.
The only mechanism whereby a body could be made to vibrate is from the energy in the oscillating string and since the physical laws of the universe are 'universal' in nature - they also must apply here too and the act of sharing that energy can only diminish the sound production.
Any time you absorb a frequency or 'tone', the unattenuated frequencies or 'tones' may sound larger or louder and thus people think the body is adding to those perceived sounds when it is actually taking away sounds on the other side of their listening spectrum.
Hollow body instruments are included in the same physical laws of the universe, but have other harmonic and orders of magnitude and frequent-resonance factors that come into play; these are not as evident in a slab-body instrument.
The laws of the universe are inviolate - except to those who falsely believe otherwise.
*NOTE: First Law of Thermodynamics
The first law of thermodynamics is often called the Law of Conservation of Energy. This law states that energy can be transferred from one system to another in many forms; it can not be created or destroyed.
Footnote 1: ATTENUATE: to become weaker or to be made to be weaker in strength, value, or magnitude.
Nutshell observation: Wood taketh away, not addith-to the sound of you bass. SurferJoe 1:1