Singing this Note is IMPOSSIBLE!

Very interesting!  You have touched on a subject, that has some controversy surrounding it, in the Audiophile field.   Why do speakers with fairly small magnets driven with a vacuum tube amplifier, produce more bass, than a transistor power amp driving speakers with large magnets and stronger magnetic fields.  At the resonant frequency of the speaker, the speaker cone and voice coil are out of phase by about 90 degrees of the voltage driving them.  Tube amplifiers attempt to supply a current proportional to the input signal voltage, (to the amp),... because the current is maximum when the voltage crosses the zero voltage crossing, and the older style tube amps with coupling transformer, and lower negative feedback, have a lower damping factor, the bass at the resonant frequency comes through fine, even though the speaker exhibits it's highest resistance at the resonant frequency.  In a  transistor amp where the output voltage tends to follow precisely the input voltage, the 90 degrees out of phase signal at bass resonance to the speaker, provides negative feedback to the speaker, just as the cone is going towards it's maximum excursion,  and damps the speaker which ceases to be driven, and is beginning to generate a back electromotive force.  In addition, as the Voltage signal from the amp goes to zero, the current also drops to zero so the speakers motion in response also tries to go to zero.  Looking at the phase relationship when the output signal is highest, the mass of the speaker cone and voicecoil, has enough inertia as a whole, at low frequencies such that they are just starting to move, even though the voltage applied to them is at it's peak.  So even though two amps  (one tube, and the other transistor) may seem to have identical frequency response, and power driving a resistor, the tube amp, when checked with a microphone, will deliver more bass into a fairly resonant speaker, (high "Q") with identical voltage output (measured with the resistor load).  Transistor amps tend to always deliver the same voltage output as the input, while tube amps also show a loading effect, meaning the output voltage drops under load, and the voltage and current output will increase, (also out of phase) into a highly reactive load,.. this is also partly the result of how hysteresis in an output transformer can release energy, when the signal applied to it crosses through zero after having been driven to the point of "charging" the transformers iron core.  All in all The transistor amp behaves more like singing directly into the PVC pipe (pressure loading), versus singing across it, like it is a flute, which is more the way a vacuum tube amplifier would behave.