"Tone.js is a Web Audio framework for creating interactive music in the browser. "
In tone's transport object, the default number of ticks (subdivisions, or ppq) is 192 when the bpm value is at 60. It is proportional to bpm, so at 120 bpm, number of ticks (subdivisions, ppq) is 384.
Why was this number (192, or 384) chosen, instead of something like 200 (and 400 for 120 bpm)? Does it have any particular properties, that make it more suitable to be the default number of ticks for the default bpm?
PPQ (Pulses Per Quarter-node) is often in values which are divisible by both 2 and 3 which allows it to accurately represent both triplet rhythms (divisions of 3) and duplet rhythms (divisions of 2) which are pretty common rhythmic subdivisions.
For example, with a PPQ of 6, the quarter note could be divided in three ways: by 2, 3 and 6. Those divisions would yield an 8th note (dividing the quarter in 2), a triplet 8th note (dividing by 3) and a triplet 16th note (dividing in 6 equal parts).
The higher the PPQ number, the more divisors (and therefore the more rhythms that it can represent with whole number ticks). A PPQ of 200 or 400 would be good at representing quintuplets (divisions of 5) and duplets since it's divisible by 5 and 2 many times, but wouldn't be able to be evenly divided by 3.