I studied Latin in high school, but it’s been a while.
My question is this: Can you use a noun as an adjective if you’re talking about one thing made of another thing? Or do you have to put the noun in the genitive case?
I’m trying to make a pun describing a person literally made out of sound. Is it legitimate to say:
“Mens sonita in corpore sonito.” (A sound-mind in a sound-body).
Or must I say:
“Mens sonitūs in corpore sonitūs.” (A mind of sound in a body of sound.)
The genitive of material is usually used to limit the composition of another noun, e.g. gladius ferri - “an iron sword/sword of iron”. This is the preferred construction. I also think you should use the closer-to-the-pun sonus, -i here: mens soni in corpore soni
Mens sonita is literally “a mind having been sounded”, perhaps not quite what you’re after.
Thanks. 
Just out of curiosity, is there any difference in meaning between “sonus” and “sonitus”?
Besides the declentions, sonus, -i is the basic “sound”, while sonitus, -us is more like “repeated/loud sound” (the -ito suffix in Latin is called a frequentative used to indicate repeated or cumulative action, much like how the -le or -er ending transforms verbs like “crack” and “flick” into “crackle” and “flicker”).
Thanks again.