RE: Casavants Bellevue MIDI pieces to download?
My website https://midimusic.github.io
has around 600 Estey organ files archived in e-roll format. It also has eplayOrgan which can play these files and translate them to play on your Cassavants Bellevue organ.
You need to download and install eplayOrgan and get it working to play some of the Estey music. Then download from the website and import your organ into eplayOrgan. You will then be able to play and translate the e-rolls to your organ's format. The resulting files will play correctly on your organ.
This procedure will work with any organ that eplayOrgan can play.