Please explain what is going on with the letter aleph in certain places in Tanakh (e.g. the second to last word of Devarim 3:12, the first word of Tehilim 34:10) where the aleph contributes neither a consonant nor a vowel sound. In these instances, the word is pronounced as though the aleph were not there at all.
My Feldheim Simanim Tanakh colors these alephs in gray and quotes the "Mesora Rabta" as saying that there are 48 words that contain an unpronounced aleph. I would be interested to learn more about this phenomenon. Why are these silent alephs present at all? Are there any other Hebrew letters that can be completely silent in this way?
(I'm not familiar with the work "Mesora Rabta", so a pointer to that would also be helpful.)