New floor joists in the log cabin, how would you have done it? Stuck...
Building acoustics is quite complicated. To sort out the conditions, one has to look at the current frequencies (and thus wavelengths). 340 divided by the frequency (in Hz) gives the wavelength (in meters). Resonance in building parts can occur in various ways. Everything depends on the wavelength. My perception of rock music is that it involves relatively high frequencies (several thousand Hz), and in that case, I don't think the current construction should pose a problem. It's more challenging with low-frequency sounds. The biggest challenge is probably ensuring that the neighbors are not disturbed. Then you benefit from the timber in the outer walls, which provides a fairly heavy construction.
Forgot to mention that for the music experience itself, the room's acoustic conditions are more interesting. Live music requires longer reverberation time than is common in homes. Above all, one should avoid materials (textiles, padding, etc.) that absorb the high-frequency tones to achieve a balanced sound image. The floor with partially unfilled sections can function as diaphragm absorbers for low-frequency sound, which is positive!