Ida fragrans, a native of Ecuador and Columbia where it grows at around 5000 ft., blooming in the greenhouse. True to Oakeley's description, it has the fragrance of hyacinths at night (yes, I had to go out into the greenhouse at night to smell it to see if it was really true!). Much thanks to Dr. Henry Oakeley for the very helpful description (and the autograph on my copy of Lycaste, Ida and Anguloa). Notably, the picture of Ida fragrans in Orchidencyclopedia.com appears to be of something else (which ultimately forced me to look things up in Oakely, which I should have done in the first place).
A close-up of the lip detail here, showing the 5 keeled callus (which is mainly visible if you view it from above).