HISE is an open source framework for building sample based virtual instruments.
A highly performant Disk-Streaming Engine that allows you to stream hundreds of samples in parallel. Powerful .xml sample-mapping and HLAC-compression-algorithm included.
A flexible DSP-Audio Module system that lets you combine Sound Generators, Modulators and Effects in a tree-like architecture for maximum efficiency.
A handy Interface Designer that makes it easy to hook up an interface with customizable UI Components and convenient Floating Tiles.
Build upon the HISE architecture, include external libraries and get the most out of the Engine with C++.
Export and Compile your HISE instruments and plugins as VSTi, AU and Standalone for all major OS platforms and DAWs.
Source: HISE Documentation
SFZ opcode support for import can be seen from source code.