EXCLUSIVE

Lamar Odom couldn't have gotten on a cross-country flight without Kanye West's help, which is why Lamar was determined to get on a flight to NYC ... TMZ has learned.

Sources close to Lamar tell us when he was in Cedars-Sinai hospital ... Kanye religiously showed up to visit and frequently played rough cuts of his new music for Lamar. He started remembering specific lyrics, which was one of the early signs LO's condition was improving.

We're told Lamar is well aware of the role 'Ye's music played in his comeback.

He told Khloe how important it was for him to be at Thursday's show in NYC ... to show Kanye how much he "loves and supports" him.