The EAMIR SDK for Max/MSP/Jitter allows users to build their own custom composition and performance applications for use with just about any control interface. Included in this SDK are the Modal Object Library, a collection of objects for creating and working with diatonic modes and harmony within Max, and the V Objects helper abstractions.
It was developed by V.J. Manzo (http://vjmanzo.com) as part of the EAMIR project (http://eamir.org).
The development build of the EAMIR SDK is available here and the official releases are available through Max in the "Package Manager" (recommended).