Pied Piping
Part of the spell description is below. It says that affected creatures can take no actions other than listening and following - does this mean they are not allowed to talk or communicate with anyone around them? Can they use hand signals, point, wave, etc?
The duration is concentration + 1 round per level. It also says targets in the area of effect continue making saving throws until they fail, and new targets entering the area also need to make saves until they fail. However, my question is this - what if I cast the spell and the very next round I stop concentrating. According to the description the spell continues for 1 round per level after I cease concentrating. So therefore, do the targets (new and existing ones) still make saves each round until the 1 round per level duration is used up? And what does the last line of the spell description mean - i.e. what is the difference between the spell ceasing and the spell wearing off? Aren't they one and the same?
Duration concentration + 1 round/level
...Affected creatures can take no actions other than listening to your music and following you if you move. Those entering the area while the spell is in effect must also successfully save or be compelled to come to you.
The attractive power of the spell does not cause affected creatures to put themselves in jeopardy and they have enough presence of mind to avoid or negotiate around obstacles and other perilous hazards. If unable to approach or follow you without endangering themselves, they simply wait, swaying to the music, until you pass out of range, at which point they regain their senses after 1 round/caster level. If circumstances change once you move out of range, making it possible for affected creatures to resume their attempts to get near you they do so, and, if they manage to return to within the area of the spell before it wears off, the spell continues as normal. If attacked, affected creatures can take defensive measures, even going so far as to avoid existing threats by moving out of the area of the spell, but cannot make attacks themselves or take any other actions until the effects of the spell wear off. The effects of the spell persist for 1 round/caster level even after you stop concentrating. Once the spell ceases, the affected creatures continue to stay near you until the effects of the spell wear off.
It says that affected creatures can take no actions other than listening and following - does this mean they are not allowed to talk or communicate with anyone around them? Can they use hand signals, point, wave, etc?
No action. At all. Just Listen, Follow and probably anything done passively, like looking or breathing.
do the targets (new and existing ones) still make saves each round until the 1 round per level duration is used up?
Yes.
what is the difference between the spell ceasing and the spell wearing off?
Ceasing = you stop. Wearing off = they get rid of it, either because you stop or something is countering the effect for them. It's effectively the same in most cases.