Advanced Gtk+ Sequencer is capable of doing multi-channel editing, it contains an automation editor and you might want live export to audio files. There are sequencer machines as well a fully featured notation editor. Supporting copy & paste, resizing audio channels or align in-/output pads. Supported plugin formats are LADSPA, DSSI and Lv2. Output to soundcard is done by ALSA, Pulseaudio or JACK Audio Connection Kit. MIDI input can be performed by connecting a keyboard.