If you are looking for the original FM7 experience on a modern 64-bit system, you must use "bridging" software.
The story of the Native Instruments FM7 is a tale of digital resurrection. It is the plugin that brought the iconic sounds of the 1980s into the modern era, only to become a "lost relic" itself due to the evolution of computer architecture. The Resurrection of FM Synthesis Native Instruments Fm7 64 Bit
For current music production, and is often on sale as part of NI's Komplete bundles. If you are looking for the original FM7
If you see a reference to "FM7 64-bit," it usually means one of two things: Native Instruments Fm7 64 Bit