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2004-05-08 13:36:45

What you will need for this bite-sized example


It can take a while to realize the full power of JACK. In this example we'll explore some possibilities for interconnections. Let's dive straight in. Launch JACK from the AUDIO->DEEJAY menu, if it isn't already running. All the programs we'll be using come from this same menu. You might also bring up the Connection Panel, as we'll need it shortly. We'll be bouncing around quite a bit, so this is a great time to try the Alt-1, Alt-2, etc. shortcuts to switch workspaces.

a Hydrogen screen capture On another Workspace, launch Hydrogen. This drum machine is very powerful and offers its own world of possibilities. For this example, we just need a basic looping beat, so let's do an Open Demo, and select GM_kit_Jazzy.h2song. The demo song is just for convenience, as there are lots of other ways to get a basic looping beat in d:b. For example, grab a loop sample and load it in terminatorX. (If you need drum loops or drum samples, check out DooleyDrums.com.) A SoundTracker module would be another idea. All that is needed for this example is a repeating loop. If you make any substitutions, just make sure it is configured to play through JACK, and adjust the next steps accordingly.

Jump to another Workspace and launch JACK Rack, an effect processor based on LADSPA. It might look rather empty at first, but we'll take care of that, soon. So far we have JACK, Hydrogen and JACK Rack. Let's drop back to the JACK Connections panel and wire things together.

Jack Audio Connections Panel

By default, Hydrogen made a connection to the default output, but we want it to go through JACK Rack, instead. Select Hydrogen on the left and alsa_pcm on the right, and click the Disconnect button. Now connect Hydrogen to jack_rack, and jack_rack to alsa_pcm as shown. Jump back to Hydrogen and hit play, the green triangle marked button near the top left corner.

a JACK Rack screen capture Now switch back to JACK Rack.

Click the Add button and select Time->Flangers->DJ Flanger. Click Add again and select the Bode frequency shifter.

Click the Wet/Dry button in the frequency shifter and set the control that appears to about the half-way point by pulling it to the left. Click the Enable buttons on both effects. Now grab the Base Shift control, and pull it around, and jam away.

This is a pretty extreme example, but JACK Rack is capable of much more subtle enhancements. The only limits are your imagination (and maybe your CPU and memory, but this doesn't require state of the art hardware, either.) Just a few more words of advice to try and make your experimentation more pleasant. Some effects are not Real Time (RT) so applying them to a playing stream doesn't work. Don't despair, there are plenty more. Also, be careful about your listening levels when playing with the unknown. If things don't work right, digital breakup noise can be quite unpleasant and no doubt can be rough on speakers, as well as ears.

a second JACK Rack screen capture One more tip. You can run multiple JACK Racks. The number at the top of the rack window matches the number shown in the connection list. Let's put this to use on the patch we've already developed. Launch a new JACK Rack. To it add Amplitude->Amplifiers->Simple amplifier, and Time->Phasers->Auto phaser. Set the controls close to what is shown in the picture, but don't enable them, just yet.

Drop over to the connections panel and connect Hydrogen to the new jack_rack and the new jack_rack to alsa_pcm. You'll hear a second clean layer of the Hydrogen track added. Go back an enable both channels on the new rack.

another Jack Audio Connections Panel

So you've now got tons of cool effects gear, and an endless supply of patch cables that never get tangled. Oh, and did you notice, lots of it can be MIDI enabled by right clicking on a control? Dig in and enjoy!

Now you've got power. Go create something wonderful!

Article 17 was last updated 2004-05-09 17:42:09

Put JACK to work creating a techno-drum track with this bite-sized example.