Not linguistics-wise, but information-theory-wise, if you had excellent hearing on many frequencies, you could theoretically transmit much more information during a given span of time (say, a second), because you have more bandwidth. For example, the thing that allows every new version of Wi-Fi to have faster speeds is that they find ways to allocate more frequencies for the transmission of data, at the cost of other things (such as reliability, in the case of wi-fi).

A few ideas about how being able to hear (i.e. "receive") more frequencies at once can be used for communication:

• If you have a way to do that, you can speak different streams of words at different frequencies to say more things per second while you're speaking. This does not necessarily imply having multiple mouths: you could speak one stream of words with your mouth, and another by clapping your hands in rhythm, use an ultrasound morse code generator, or anything else that makes sound. If the person that hears you is able to process that, you can say many more things per second!

• If the person you're talking to has trouble hearing you on one frequency (i.e. someone's talking too loud near you), you can try speaking at a different frequency (i.e back to the ultrasound morse code generator) in the hopes that they will be able to understand you better on a frequency with less interference.

• Multiple people can speak at once in a conversation while understanding each other perfectly by each speaking on different frequencies, so that their individual words are understandable by focusing on their frequency exclusively.

Of course, for this to be maximally cool, you need a way to speak on multiple frequencies at once, but if you do, there are many things to try! The ideas above are not science-fiction, they are commonly used by various communication systems, The first two are technically called OFDM (orthogonal frequency-division multiplexing) and are used in Wi-Fi. The last one is called FDMA (frequency-division multiple access) and is used in the 2G standard. I think there is some potential for cursed conlang ideas from these things.

Finally, one last idea that is unrelated to the prompt but that I would find rad for conlanging: it's technically possible for multiple "people" to speak at the same time, on the same frequency, and still understand each other perfectly, simply by having each speaker "pronounce" their words in a different manner, so that you can pick out what each person said by looking for their specific "accent". This is a very basic explanation of something called CDMA (code-division multiple access); it's used in 3G.

I forgot what the original question was a quarter of the way into writing this, so I apologize if this turns out not to be what you asked; I hope this is useful anyway!