A "Tenor" is a singer with a fantastic voice and he/she can sing songs with really high musical notes. The " DO de pecho" is the highest note that Tenors can do ( it is usually taking place at the end of the songs) and you have to swell your chest as much as you can with air because of that note. The sound is powerfull and in a high volume leve. So, in this sentence, the meaning is like, "The tenor made his dairy high and powerfull sound (like the lions "roar") but the lion didn't pay attencion of him"