Also, note that period = 0 is the same as period = 1. This is mentioned in the YM2203 datasheet. However, this does NOT apply to the Envelope period. In that case, period = 0 is half as period = 1. [https://github.com/mamedev/mame/blob/master/src/devices/sound/ay8910.cpp Source]
The tones, the noise, and envelope are never halted. All of them are continually active whether or not they're connected to an audible output.
Things that have been verified not to halt things: [https://forums.nesdev.org/viewtopic.php?p=236745#p236745 Source]
* Volume 0 does not halt tone or noise
* Tone disable bit does not halt tone
* Setting all 3 noise disable bits does not halt noise
* Clearing all 3 channel volume envelope bits does not halt envelope
* Period value of 0 does not halt any of these (treated as period 1 in all cases)
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