According to Pam, Oscar can sing when she plays the piano, he can hold a note, and even do a vibrato. Oscar started singing a year and a half prior to the audition in Pam's living room while she was playing the piano, and they have been working together ever since.
Oscar & Pam Singing Dog Wins America's Heart - America's Got Talent 2018
Oscar and Pam's Judge Cuts performance in Episode 1307 consisted of playing the piano and howling "singing" a song. Mel B buzzed the act. Their performance was not strong enough to advance to the Quarterfinals, eliminating them from the competition along with Lilly Wilker and Patches.