Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
Digital Level Meter - Display sound level
Ampire - State Space Modeled guitar amp/cab/stompbox simulator.
AudioTool - Whether you want to make music for the club, or you're aiming to put a few tracks to a film, Audiotool is a website geared towards putting the mixes at your fingertips. Read more about AudioTool.
TH-U - World class guitar amps and effects for PC and Mac
Youlean Loudness Meter - Find your audio's true perceived loudness to prepare for TV and streaming services.