You can't post raw audio to Twitter directly. It sucks.
Sure, you can post links to audio, but it's not quite the same.
Here's a couple of Linux one-liners which will turn audio into simple video suitable for uploading to social media.
This converts audio to a waveform:
ffmpeg -i input.mp3 -filter_complex "[0:a]showwaves=s=640x480:mode=line,format=yuv420p[v]" -map "[v]" -map 0:a -c:v libx264 -c:a copy output.mkv
How it looks
Aha! Managed to catch the whole call.— Terence Eden (@edent) January 7, 2020
🤖 "Dear customer, we charged you £299 from your account. If you want to cancel please call 8081896207"
Obvious spam call - see https://t.co/7eARNhM0Y6 pic.twitter.com/LWAI7FNw44
This takes a single image and adds it to the audio:
ffmpeg -loop 1 -i image.jpg -i audio.mp3 -c:v libx264 -tune stillimage -c:a copy -pix_fmt yuv420p -shortest out.mp4
How it looks
Oh no! Looks like HMRC have a warrant out for my arrest! Well, according to this "official" sounding robot.— Terence Eden (@edent) December 12, 2019
More seriously, mobile networks need to clamp down on CLI spoofing. I get the legitimate need for it - but it is subject to so much abuse. pic.twitter.com/MH9BAHOyUe
That's it! If you know of a more efficient way to do it - shove a comment in the box.