I'm looking for a way to apply manually controlled effects, like echo or pitch change, or equalizer, to the entire sound output in Ubuntu. I'm thinking about something similar to what Creative SB Live! software can do on Windows. The effects should affect all applications playing sounds in the system, and preferably should be controlled via GUI. Should I be investigating the direction of ALSA plugins (which I know nothing about at the moment)?
Pulseaudio supports some LADSPA plugins.
sudo aptitude install rlwrap swh-plugins rlwrap pacmd # equalizer load-module module-ladspa-sink sink_name=ladspa_out plugin=mbeq_1197 label=mbeq control=11.621622,10,4.594594,2.702703,0,0,-1.621622,-0.270270,-5.405406,-3.513514,-8.648648,-5.675676,-4.054054,1.351351,9.189189 # volume compression load-module module-ladspa-sink sink_name=sc4m plugin=sc4m_1916 label=sc4m control=1,1.5,401,-30,20,5,12 set-default-sink sc4m