@Alex-Kushleyev I tested it and it works nice (I didn't test the 255 but I expect that should work). I already figured that the frequencies are now multiples of 10Hz with some minimum value (I don't know which one but at least below -p 10 I don't hear the frequency drop anymore). So it ranges up to 2550Hz. And I think you also adjusted the duration to be multiples of 10ms to match with the format of the ESC parameters?
Regarding the usage change, I understand if you don't want to create a breaking change. But I think it would be good when the print_usage matches with the actual use. It took me some trial and error to get it working. Maybe also an idea to use -f for the frequency because -p refers to period which is not correct anymore and it is now already changing the functionality of the tone generation (you could even let -p in it to keep it backwards compatible but that maybe makes it unnecessarily complicated). And also good to allow the ESC mapping to go up to 15.
For us it is sufficient to use the startup tone. But I played around a little bit with the tone generation and if you use it using the qshell commands you need to wait the duration of the tone to send a new tone (as the qshell command immediately returns and it doesn't accept a command while the sound is still playing) which makes it difficult to get the timing right in playing a tune. I don't know what the end goal should be of this but if it is playing custom tunes using the commands this is something to keep in mind I think. I had some fun trying to play the Imperial March on the ESCs which kind of works but not as smooth as the startup sound can play.