Could a ghost Parselmouth open the Chamber of Secrets?

Question

Suppose that, as with some of the other founders, a descendent of Slytherin came back to Hogwarts as a ghost. Could they open the Chamber of Secrets?

Answer 1

Yes, ghosts can open the Chamber of Secrets.

Opening the entrance to the Chamber of Secrets requires only speaking in Parseltongue. There are no other barriers to entry - it is opened by a password in Parseltongue.¹

“Harry looked back at the snake, willing himself to believe it was alive. If he moved his head, the candlelight made it look as though it was moving.

‘Open up,’ he said.

Except that the words weren’t what he heard; a strange hissing had escaped him, and at once the tap glowed with a brilliant white light and began to spin. Next second, the sink began to move. The sink, in fact, sank, right out of sight, leaving a large pipe exposed, a pipe wide enough for a man to slide into.”
_{^{- Harry Potter and the Chamber of Secrets, Chapter 16 (The Chamber of Secrets)}}

Ghosts still have the ability to speak, so it logically follows that a ghost who can speak Parseltongue can open the Chamber of Secrets. A ghost also should be able to release the basilisk, since releasing it only requires speaking a password in Parseltongue as well. The Tom Riddle from the diary, in fact, released the basilisk while not fully a solid being, still a memory pulling life from Ginny.

“He cast an amused eye over Fawkes and the Sorting Hat, then walked away. Harry, fear spreading up his numb legs, watched Riddle stop between the high pillars and look up into the stone face of Slytherin, high above him in the half-darkness. Riddle opened his mouth wide and hissed – but Harry understood what he was saying.

‘Speak to me, Slytherin, greatest of the Hogwarts Four.’”
_{^{- Harry Potter and the Chamber of Secrets, Chapter 17 (The Heir of Slytherin)}}

Also, controlling the basilisk only requires the ability to speak to it in Parseltongue, so a ghost should be able to command the basilisk as well. As further proof, not-fully-solid Tom Riddle is able to command it.

“He knew what was happening, he could sense it, could almost see the giant serpent uncoiling itself from Slytherin’s mouth. Then he heard Riddle’s hissing voice: ‘Kill him.’”
_{^{- Harry Potter and the Chamber of Secrets, Chapter 17 (The Heir of Slytherin)}}

Therefore, a ghost would be capable of opening the Chamber, releasing the basilisk, and then commanding the basilisk to its will.

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¹ _{Examples of other entrances protected by passwords in Hogwarts show that all that needed to get through is the password. Harry is able to get into the Headmaster’s office by guessing multiple possible passwords and stumbling onto the correct one on his ninth attempt.}

_{“Harry had walked right past the stone gargoyle guarding the entrance to Dumbledore’s office without noticing. He blinked, looked around, realised what he had done and retraced his steps, stopping in front of it. Then he remembered that he didn’t know the password.}

_{‘Sherbet lemon?’ he tried tentatively. The gargoyle did not move.}

_{‘OK,’ said Harry, staring at it. ‘Pear drop. Er – Liquorice wand. Fizzing Whizzbee. Drooble’s Best Blowing Gum. Bertie Bott’s Every Flavour Beans … oh no, he doesn’t like them, does he? … Oh, just open, can’t you?’ he said angrily. ‘I really need to see him, it’s urgent!’}

_{The gargoyle remained immovable. Harry kicked it, achieving nothing but an excruciating pain in his big toe. ‘Chocolate Frog!’ he yelled angrily, standing on one leg. ‘Sugar quill! Cockroach cluster!’}

_{The gargoyle sprang to life, and jumped aside. Harry blinked.”
^{- Harry Potter and the Goblet of Fire, Chapter 29 (The Dream)}}

Answer 2

In Deathly Hallows, Ron opens the chamber by imitating the sounds Harry had previously used to open the locket:

Harry’s eyes dropped to the objects clutched in Ron and Hermione’s arms: great, curved fangs torn, he now realised, from the skull of a dead Basilisk.

‘But how did you get in there?’he asked, staring from the fangs to Ron. ‘You need to speak Parseltongue!’‘

He did!’whispered Hermione. ‘Show him, Ron!’

Ron made a horrible, strangled hissing noise.

‘It’s what you did to open the locket,’he told Harry apologetically. ‘I had to have a few goes to get it right, but,’he shrugged modestly, ‘we got there in the end.’

He is not a Parseltongue and does not understand the meaning, which implies that the Chamber simply responds to the sound pattern, and that a ghost could therefore open the Chamber.

Not so clear whether they would be able to command the Basilisk.