>> susan benedetto: i thought it was a triumph, really. it's, like-- you know, climbing mt. >> tony bennett: i don't know what you mean. >> cooper: i saw you at radio city. you did a great job. >> tony bennett: oh, thank you very much. >> cooper: tony had no memory of playing radio city at all. is this a sad story, tony bennett's last performance? >> lady gaga: no. it's not a sad story. it's emotional. it's hard to watch somebody change. i think what's been beautiful about this, and what's been challenging, is to see how it affects him in some ways, but to see how it doesn't affect his talent. i think he really pushed through something to give the world the gift of knowing that things can change and you can still be magnificent. ♪ your golden sun will shine for me! ♪ ( cheers and applause ) >> alfonsi: at 95 years old, tony bennett continues setting records. his album with lady gaga, released this past fall, is up for six grammy awards, including album of the year. he is the oldest performer ever nominated in that category. ( ticking ) >> anderson cooper on witnessing what wa