Shape-shifting is a hard work and takes long time and a lot of preparation to achieve… Fully
However (ive dealt with a lot of Shamanic things)
The beginning will always be creating deep bonds with in this case im talking about animals (im not sure if you want to shape shift into other things but animals)
But if its for animals… we can always create / develop connection to them, they want that, human perspective and respect towards the power of animals is what havocs that bridge, so when we approach it energetically and with respect they promptly answer.
To not make this comment long just read about ways to connect to the totem of the animal (their spiritual energy)
Also check the bone series available in the Sapien Shop or i think they are all in the Sound Weave one. See if you are called to initiate with any of those.
The Dolphin totem is on Gumroad (i have it 
) and there are a few on youtube on dream seeds like the wolf or whale experience.
Also the The Precarious Pinoline
Can push the opening of that bridge faster and easier
And last this NFT:
Hides you from others to see you, not saying you would use this When trying to shapeshift but right after experimenting going into the world just so you feel confident no one is picking up on you and your “shape” and energetically. Just to give you confidence so you can try more and more until you proove or believe you are not seen as the You now.
As for the singing whistling
The Divine Voice Nft (Private Project turned Public)
And there is one to improve the voice too on youtube