Kinda yes, but you're adding your own into it.
Sound is a energy form, it's not a thing, it is a energy wave which makes things move, moving thing can be any material which contains particles, in my example I used diamonds.
Relatively observing this phenomenon you know at solid material like i.e. Steel will carry sound wave thru it, this travel will happen by particles of steel colliding each other, physical movement of particles.
Same thing is when sound is traveling on plain air, same thing particles colliding each other and this physical movement carry wave form of sound energy.
And same on water.
And same on any material which can carry sound energy wave, which is a real physical energy.
This same happens on diamonds too.
So if you believe at air is soft because it can transfer sound waves, then will every other material be also soft because the reason for sound wave carrying capabilities is identical particle movement, no difference in actual physical action, just difference in material.
This lead to simple conclusion on relative perspective of material softness, sound energy wave is able to bend/push/stretch material so it can't be hard because it changes it form, so it must be soft.