Unlike earlier models of Pitch to MIDI converters by various manufacturers, the Axon does not use a frequency conversion method (counting cycles of the string) to accomplish the MIDI conversion.
This earlier method, of counting and comparing cycles, has some rather significant limitations, due to the physics of sound. The most troublesome limitation of these earlier conversion attempts is that the delay time between an audio event and the output of a MIDI signal essentially doubles when the pitch drops an octave.
This means that A-220 (2nd fret, G string), as an example, will take approximately twice as long to be converted as A-440 (5th fret, High E), one octave up. A-110 (A string open) on the other hand, can take up to four times as long as A-440.
As most of you have already experienced, this can mean tracking which is marginal at best on the lower strings of a guitar. Also, this method can be more easily fooled by prominent harmonics and other "non fundamental" partials, and can lead to inaccurate recognition and "ghost notes" (ones of very short duration).
(Bass? As my friends in Brooklyn would say……Fughedaboudit!)
Blue Chip Music Technology, however, has pioneered a new proprietary method which uses a sophisticated neural net (fuzzy logic) to "recognize" the pluck transient of an incoming signal, and compare it to events stored in it’s neural net. The neural net has received extensive training in the recognition of these transients, and "learns" how to be more accurate during this training. It can even interpolate between two known events when presented with something it hasn’t seen before.
The pluck transient is a percussive spike at the beginning of a tone which occurs before the string even settles into a periodic vibration. This spike provides information about where the string is being fretted, and where the string was plucked, if you’ve got a way extract this information. The Axon uses a high speed RISC processor and patented neural net technology to do so.
It is by using, analyzing, and recognizing this pluck transient that the Axon units achieve their terrific tracking performance, as well as being able to offer such powerful features as FRET SPLIT, PICK SPLIT and PICK CONTROL.