Thank you for your advice. My vet did tell me about the increase in vocalization because of my cat's age. This time it was my problem, I forgot to add water to his water fountain. He sure told me! I will never forget again.
Sometimes when a pet becomes elderly and does begin to show signs of dementia, they will vocalize repetitively. This is true in both dogs and cats. The first thing you can do is try to distract the pet from the behavior, as you have with petting it or holding it. Unfortunately, this can sometimes lead to the pet vocalizing just to get you to hold it. You might try distracting you cat in another way, perhaps give it a little bit of some very tasty treat or change its location by picking it up and placing it in another spot.
If the behavior continues and you can't distract your cat from vocalizing, I would suggest seeing your veterinarian to see if there is any medication he/she would feel comfortable prescribing to decrease your cat's anxiety.