Guru is a Renoise tool created by me for editing sounds on external hardware synths via MIDI. It provides a generic user interface for editing the parameters of the synth, and let’s you store them as patches, that can be restored later on.
Guru also saves the patches with the song, so when you re-open a song synths and the patches you were working with when you saved it are restored.
All the parameters are MIDI assignable, so you can use it to map any MIDI controller to the synth. For example the Korg MS-20 Legacy Controller.
Guru supports various synths like: Roland JX-8P and MKS-70, Roland Juno 1, Juno 2 and MKS-50, Yamaha DX200, Novation Drumstation, Korg DW8000 and more.
The parameters of a synth are mapped using a “synth definition”, which is a file that tells Guru which parameters are available and how the synth communicates. You can, with not too much effort, create these yourself to support any hardware you wish (given it supports editing via MIDI).
Download and read more at the Renoise site.
Here is documentation.