Stereo could be thought of as two joined mono tracks with the first one assigned Left and the second one assigned Right.
Quadtereo is the concept applied recursively; two joined stereo tracks. Four channels: LL, LR, RL and RR. Because joining tracks is required for that Nyquist multiply script to work, allowing any two tracks of the same type to be joined leads to this. To convert quadtereo to stereo, the LL channel contributes 50% to the left channel, the LR channel contributes 1÷3 to the left channel and 1÷6 to the right channel, the RL channel contributes 1÷6 to the left channel and 1÷3 to the right channel and the RR channel contributes 50% to the right channel.
Octereo (LLL, LLR, LRL, LRR, RLL, RLR, RRL, RRR) and hexadecereo (LLLL, LLLR, LLRL, LLRR, LRLL, LRLR, LRRL, LRRR, RLLL, RLLR, RLRL, RLRR, RRLL, RRLR, RRRL, RRRR) is what happens if this recursion continues. Sixteen speakers arranged in a hexadecereo formation would form a circle. Indeed Audacity doesn’t support this kind of audio, although it can be simulated. Sphereo is when speakers are arranged in a sphere formation, covering all directions. Converting a top or bottom channel of sphereo to hexadecereo would result in, you guessed it, imaginary number samples. This is all mathematical.