The phrase all together (two words) refers to people or things gathered in one place. The adverb altogether (one word) means entirely or wholly.
Examples:
When 50 Elvis impersonators appeared all together at Windsor Palace, the queen observed that this was "altogether inappropriate."
Practice:
(a) The clowns stood ______ at the front of the chapel.
(b) Despite their painted smiles, the clowns' sorrow was ______ clear.
