Fillmore is described as 'multitrack audio recorder/editor for GNOME, based on GStreamer and Gnonlin' and is a Audio Editor in the Audio & Music category. There are more than 10 alternatives to Fillmore for a variety of platforms, including Windows, Mac, Linux, Android and BSD. Most alternatives are Audio Editors and Audio Recorders. The best alternative is Audacity, which is both free and Open Source. Other great apps like Fillmore are Tenacity (Free, Open Source), AudioMass (Free, Open Source), DarkAudacity (Free, Open Source) and Radium (Paid, Open Source).
Audacity is free, open source software for recording and editing sounds. You can use Audacity to record live audio, convert tapes and records, edit sound files, change the speed or pitch of a recording and much more.
AudioMass lets you record, or use your existing audio tracks, and modify them by trimming, cutting, pasting or applying a plethora of effects, from compression and paragraphic equalizers to reverb, delay and distortion fx.
DarkAudacity is a build/fork of the the well known free sound editor, Audacity, customized with a darker, more modern theme - and a few small tweaks. The audio engine underneath is the same audio engine. The same code powers it. Like Audacity, it is completely free.