qtractor
The Jack Audio Connection Kit (JACK) for audio, and the Advanced Linux Sound Architecture (ALSA) for MIDI, are the main infrastructures to evolve as a fairly-featured Linux Desktop Audio Workstation GUI, especially dedicated to the personal home-studio.
Latest reviews
It's the second time I installed it and try to make it output something...While everything else is working very good, keyboard, lmms, vlc playback, etc. This program never ever start without giving error messages. I installed Jackd, qjackctrl, no error message from both...give up.
Qtractor 0.7.7 is out since April 2016. But also the 0.5.11-version from 2013 (LinuxMint 17.n xfce, repository) has the very flexible bus system, no track limits, no plugin limits and all advantages of JACK audio-deamon (adjusting latency, USB-audio, sample depth, etc). CALF PluginPack, fluid-soundfonts and some DSSI-Instruments & Synths from Linux Mint's repository made my DAW complete! For notation or Tabs, I export midi tracks to musescore or Tux-Guitar. For surgically wave editing (repairing waves), I use audacity. Workaround to deblock LinuxMint's native PULSE AUDIO (multimedia audio daemon) after using JACK (professional audio deamon): Open taskmanager, killing jackd... (sometimes also jackdbus). After 2 seconds, Mint's pulseaudio works fine again. Hardware: USB compliant audio interfaces. Update March 2019: There's a switch in a newer Jack/Qjackctl: "Shut down JACK" after shutting down Application. No need for my workaround anymore!
Great Sequencer! Already very useable, and even more promising for the future.