Dan Jacobson wrote:
Gentlemen, I have made http://jidanni.org/comm/radio/programs/selcal :
generate ICAO SELCAL tones just like on HF aviation radio using xmms
on GNU/Linux. Purpose of this program: bring the sounds of air
traffic control into one's living room to impress guests, I suppose.

Air traffic control doesn't use selcal tones. They're pretty much
limitted to the ARINC frequencies.