sendAudio - mkotb/Telegram-Errors GitHub Wiki

If not provided, Telegram will return there is no audio in the request

Telegram will not check if the file is valid audio but the clients will not view it properly.

If specified a negative value, it will display as 0 seconds. This duration may be ignored if the audio provided is an MP3 file. In many cases, this field may be ignored completely. An example of this is where the bot provided an invalid audio file.