This command is used to add a sprite to a moan channel. Subsequent programs ran on the moan channel will then affect it.
It is possible to add a sprite to multiple channels. When this is done, the overall effect on the sprite will be a composite of the individual channels.
A sprite can be added to the same channel multiple times, this will cause it to be doubly affected by the channel, ie where a move command would move it x pixels, it will instead move it 2*x pixels.
spriteNum is the number of the sprite to add to the channel.See also Add Viewport To Channel, Remove Sprite From Channel and Remove Viewport From Channel.
channelId is the number of the moan channel to add the sprite to.