A .png is a single static image. Audio spectrum will only effect the entire image. Either break up the image into several images or try using the puppet tool to animate the tentacles. My advice if you've you've been using AE for only a week is that you should still be following tutorials step by step. forget about trapcode.
I don't know how Form or any particle effect would help you. It sounds more like you would need to animate some puppet pins to get the legs to move. You can convert audio to keyframes and use that data to drive the movement of the puppet pins, but it's definitely not a task I would take on if you're just a week into learning AE. If you're new to AE, you should really go through this first: Getting started with After Effects
Gutter-Fish thanks a lot fot the answer. The problem is that if i use the puppet tool then i have to make every single move and that will be impossible for a song, it will take long time. You told me that audio spectrum will effect the entire image so if i divide it into 2 with tentacles and the rest of the body then i can apply the audio spectrom to the lower image (tentacles) and they will just move? I don't actually know how to apply an audio spectrum to an image.
The other problem is that if i do like that then i won't have the effect that i want. I want the tentacles moves like a wave (the real movement of an octopus) with different frequency and thats why i thought about Trapcode. With that i could put differents polar coordinate over the image and then make it move.
Szalam thanks you too for the answer. Are there some tutorial for animation like this? Actually i can't find it on YT
You could try using some distortion effect or liquify and mask the effect using the composite option in the timeline's effect attributes to confine the distortion to the tentacles. You could even try a separate masked liquify for each tentacle. But ALAS that probably doesn't much sense to you being only a week old.
The problem is that if i use the puppet tool then i have to make every single move and that will be impossible for a song, it will take long time.
After Effects has a looooong learning curve.
Yeah i know that after a week i'm not able to do anything but with some video tutorial maybe i can. In my head i know how to do it, like select a tentacle, apply a frequency in different point of a tentacle and proceed with the others. For example i saw that NCS has an audio spectrum made with Trapcode. If only i can decide every single frequency of a particle of trapcode form in a specific point of the image. Anyway i didn't understand the effect that you told me. Can you link me a video which show that? Thanks
How long will you devote to this project? If your bright these simple steps will take you a month to figure out.
1 Use low pass filter around 100 Hz to limit the animation data to a reasonable amount.a
2 Use mask tool to mask around the octopus.
3 Use sound to keyframs on the filtered file open the atrbutes of this layer to and highlet the keyframes copy them.
4 apply bitmap distortion effect to the masked octopus layer.
5 Paste the sound data keyframs in the image displacement atributes. Try different ones experiment.
you'll need to import the unflitered music layer to hear thesound and delete the filter layer after saving it
You can see how this works here: Chuck Brown Tribute
I saw the video and the effect is not what i'm expecting for...anyway thank you all for the answers, it might be long to do it and quite hard so if anyone else has some advise or video just send it to me
Having only been using AE for one week? My advice is to take the "long...and quite hard" route. If you're not willing to to do that you might want to find yourself another career path (or hobby).
Rarely are you find tutorials that tell the "easiest" way to do what you see in your head but have no clue how to do.
You need to learn the tools of the software. how stuff works & then apply them creatively to achieve what you want.
Here's the bad news: It will likely take you years of study & practice until you know the tools that well.
So get started....and have fun.