The MIDI sounds are modified by the thresholds only to a certain extent. The main purpose of the MIDI is to work as a continuous feedback to the brain. The idea of the continuous feedback is to function as a mirror that reflects everything the brain is doing. It focuses not on whether the amplitude has or hasn’t crossed the threshold, but on how much it was high or low in comparison with the target. This way, you should not expect to be able to get a yes or no response from the sounds.
There are some studies from the 90s that suggest that continuous feedback may produce a better response from the brain than contingent feedback. Brain-Trainer pioneered the use of the continuous MIDI in the late 90s. The aim of the continuous MIDI is to communicate directly with the brain and turn off any attempt of the conscious mind to figure out how the feedback is working. It works especially well for people who have a tendency to be always trying to control things. Not understanding consciously why the music is playing the way it’s playing makes the controlling mind simply let go and then the brain can respond directly to the feedback without any interference.
Brain-Trainer for BioEra MIDI feedback
Tones: The notes are based on the range of the ratios of the last X seconds (X depends on the protocol). A ratio is the amplitude divided by the threshold (slider). So, let’s say in the last X seconds the ratios ranged from 0.4 to 1.2. And let’s suppose the MIDI tones are set to play notes from C5 to C6. Then, if the current ratio is 0.4, it will play a C5. If the ratio is 1.2, it will play a C6. If the ratio is 0.8 (halfway between 0.4 and 1.2) the note will be a G5. And so on. When the current ratio is out of the range of the last X seconds, it will play the highest/lowest note and will increase the range. For example: a ratio of 1.5 would play a C6 and the reference range would change from 0.4-1.2 to 0.4-1.5.
Volume: The volume is based on the range ratio of the last 5 seconds. The same explanation for the MIDI notes is valid for the volume. Even when it passes 100%, the the idea is tell the brain “how much” it passed. That’s why the feedback is based on the ratio (continuous feedback) instead of a simple yes/no approach (contingent feedback). So if in the last 5 seconds, with 100% passing the threshold, the ratio varied from 1.1 and 2.0, that is the range on which the feedback will be based.