Here are some links to great software to help you with development of assets for RPGIAB and your game.
Voxels:
MagicaVoxel: freeware voxel editor - https://ephtracy.github.io/
Qubicle Voxel Editor: https://store.steampowered.com/app/454550/Qubicle_Voxel_Editor/ and 3D to voxel importer: https://store.steampowered.com/app/456230/Qubicle_Mesh_Module/
Anima Toon: 3D Voxel animator - https://store.steampowered.com/app/1696890/Anima_Toon_3D_Voxel_Character_Animati...
Music and Sound:
Free Online Midi Synth Editor: https://signal.vercel.app/edit
Artwork:
Aseprite animated pixel editing software: https://www.aseprite.org/
Krita: Free and open source painting program: https://krita.org/en/
Pixel Studio for Pixel Art: https://store.steampowered.com/app/1204050/Pixel_Studio__pixel_art_editor/
Voxel Model Downloads and purchases:
From Sketchfab: https://sketchfab.com/tags/voxel
Voxel Models from CGTrader: https://www.cgtrader.com/free-3d-models/voxel
Voxel Models on itch.io: https://itch.io/game-assets/free/tag-voxel
Voxel Models from Turbosquid: https://www.turbosquid.com/Search/3D-Models/free/voxel
Voxel Models from Free3d: https://free3d.com/premium-3d-models/voxel
Voxel Models from 3DMDB: https://3dmdb.com/en/3d-models/voxel/
Mini Mikes Metro Mini's city and character voxel pack: https://mikelovesrobots.github.io/mmmm/