The science of wordless spellcasting

I'm Harry Potter. I wake up in my bed, in the bedroom of a pretty normal looking modern Muggle-style house. The opposite wall, across the room and parallel to my bed, had built-in bookshelves from the ceiling down to about 3 feet off the floor. Below each column of bookshelves were three drawers.

In the previous dream, just before I woke up, a friend of mine had used the spell "fermata" to close the front door of a house we were getting ready to go into. I decided to test the opposite spell, the spell for opening things, "abierto" (I have no idea if either of these are real spells in the Harry Potter universe). I point my wand at a drawer and speak, "abierto". I mess around with my pronunciation, at first rolling my "r", then switching to a British (RP) "r". Then I start stretching out the pronunciation slowly. That's when I notice something weird.

I decide to experiment. I point my wand at the drawer, thinking the word "abierto" in my head, while starting to say "aaaah" out loud. In anticipation, the drawer begins to open. I push it shut. Interesting. Now I point my wand, think the word "automatic", and start to say "aaaah" again. This time nothing happens. Iiiiinteresting. I test it a few more times, then rush downstairs to tell Hermione.

Downstairs in the house, there are a lot of other kids (presumably other students) milling around. I walk into the small kitchen, where Hermione is making herself breakfast alone. I excitedly tell her to guess what I found out. She says "Hmmm... could it have something to do with..." (I forget what she referred to, but it wasn't remotely related.) I shook my head, smiling. Then I explained to her what I had found out, with "aaah" and "abierto" versus "aaah" and "automatic". You didn't need to say the whole spell, you just had to be focused on the right spell and begin speaking the spell.

"Woww, cool!" said Hermione, meaning I had told her something she didn't already know. And I was happy that she was excited.

[Note: This has everything to do with me currently reading Harry Potter and the Methods of Rationality.]