I can hum Jingle Bells (or 1000+ other songs, the Star Spangled Banner, Rudolf the Red Nosed Reindeer, any pop song from the last few decades, etc...). The experience of imagining the song is the same as humming it except I don't actually hum it.
It sounds like you're saying you can't hum a song or even remember one? Can't remember anyone's voice? Can't rememeber the sound of fireworks? Of cars going by?
I can’t hum songs anymore complicated than the “Happy Birthday” song (but if it plays, I’ll recognize it).
I can’t remember people’s voices in my head (but if I hear them speaking, I’ll recognize it is them).
The bang of a fireworks or a car going by is simple enough to recall. It is also generic. I might not remember the hum of the engine of a specific car, or be able to play back a specific fireworks display.
Explains why I had such difficulty singing my whole life. It must be way easier if you can just recall a song in your head and match its pitch!
Like the idea of a firework bang, being low intense vibrations, or a car horn being a high pitched short startling sound. Still can't really imagine it like I can picture things in my head, but I have an idea of the what the experience would be like.
Another fun story. I did improv comedy for a few years. One of the warm up games we played was someone would start singing a song, then another person would tag you out and sing a different song. I was bad at this game. But I have a few simple things in my back pocket to "play". Somewhere over the rainbow is one of them. The last person was doing some sort of rap, and what came out from me was a rap version, until the crowd helped correct it. I just have no idea what it sounds like other than trying to memorize if it's a high pitch or a low pitch, etc.
Regarding the inner monologue, I do have one. And it feels similar to my ability to visualize. I can control it, give it emotion per say, (not sound for me), but it isn't as strong as a memory of a dream.