Compose and record
Is it a kind of diet Ardour or an all-powerful multi-track sequencer? John Knight explores the intriguing sound editor Qtractor.
Is it a kind of diet Ardour or an all-powerful sequencer? John Knight explores the intriguing sound editor Qtractor.
For those not in the know, Qtractor is a Qt-based ( https://qtractor.sourceforge.io), Linux-only Digital Audio Workstation (DAW) designed around JACK. However, the term DAW may put readers on edge, as Qtractor was meant to be a MIDI sequencer with some DAW features, but it’s safe to say the project has gone way beyond that!
Qtractor is a big program with many components and possibilities, so we’ll barely be able to scratch the surface. Nevertheless, we can at least show you the basics so you can hit the ground running and take it further yourself. The best way of tackling this beast is probably to start with tasks of lower complexity and slowly build up to something more advanced.
Before you can get started there are a number of things to take care of. Firstly, you need to have JACK working correctly. JACK is a complex system ( try UbuntuStudio–Ed) that opens up a whole new can of worms, so we’ve given it its own separate box rather than bore you with it here. Mercifully, once JACK is set up it will retain your settings and you needn’t touch it again. Qtractor also has the thoughtful touch of starting JACK automatically for you – unlike most JACK apps.
While we’re here, please open your software manager as well, as there are a lot of plugins and external programs you’ll need along the way. Chiefly, you’ll need QjackCtl, and you should install jack-keyboard if you plan on recording MIDI without an external device.
We’ll also refer to numerous plugins and effects. Qtractor supports LADSPA, DSSI, VST, and LV2 plugins, plenty of which can be found in your software manager, but also online. We would normally be selective, but unless drive space is at a premium, you may as well install every plugin you can find!
Finally, please do a quick check of your levels before we get started. It doesn’t really matter what sound source you are using – shouting into your internet microphone will do for now – but please check that it’s working properly and will record in something you already know and trust.
Now, let’s get started…
Audio recording
The easiest task in Qtractor is recording basic wave audio, so let’s start with some simple multi-layered recording. By default Qtractor will start in an empty session, ready to go, but it will be easiest if you save now before going any further – this way you can name the project, set the tempo, and so on.
From the main toolbar click File > Save As. In the new Session window that appears you will be given fields for the name of the project, where to save it, and somewhere to write a description.
Before you click OK, open the Properties tab and you will find two important controls: Tempo, and Snap/Beat. Tempo lets you set the BPM and time signature of the project, and the Snap/Beat function will let Qtractor break your tracks down into cool workable chunks – more on that later.
Looking at the interface, there are three main panels and a messages bar. On the left is where all your tracks are listed and controlled. In the centre is the main editing field where you will record and manipulate audio. And on the right is the file list, where you can preview tracks and drag them into the editing field.
To record a new piece of audio, first create a new track. You can do this by either right-clicking in the track panel or clicking Track in the main menu, either of which will give you a menu for choosing Add Track.
This will open a new Track window. From here you can change the name of the track, choose whether you want Audio or MIDI, add plugins, and define your inputs and outputs. Don’t worry about these other options yet, for now just choose Audio from the Type field and press OK. You will now see a new track, ready for you to record in.
In the track panel you will see four buttons: R, M, S and A – Record, Mute, Solo, and Automation. Press R, which tells Qtractor which track(s) will be recording. Now from the main toolbar click the big red Record button to switch Qtractor into recording mode, and when you’re ready to go, press Play.
If all has gone as intended, Qtractor should now be recording. Press Stop when you’re done. The Backward button on the left will send the red playhead back to 0:00 and you can hit Play to listen to what you’ve recorded. If you don’t like what you’ve made, you can always press Undo.
Did you get a take you like? Time for another layer? Repeat the same process to make Track 2, but before you record, be sure to disable R on Track 1, or otherwise your new take will record over the top!
With some basic audio in place we can now start to explore some more of the GUI. Starting with the mixer, let’s play around with the levels and stereo image. The mixer icon is one of the buttons on the main toolbar, though you can also press F9.
With the mixer window open there will be three sections: Inputs on the left, Tracks in the middle, and Outputs on the right. Inputs and Outputs will control the obvious functions of any sound card mixer, but it’s the Tracks part we want to highlight. From here you can control the volume and tweak the stereo image of each recorded layer individually.
In addition to the Record, Mute, and Solo buttons carried over from the main window, below this you’ll find the horizontal Pan slider for controlling the spatial positioning of each track in the stereo image. Under this is the vertical Gain slider that will turn a track up and down, and the visualiser to the right will display track levels in realtime as you play audio.
Now to learn how to control the playhead – the red line with the triangle at the top. Pressing the backwards and forwards buttons will move the playhead around your material, although interestingly it will stop on major edit points rather than going straight to the beginning or end of the track.
If you want to move the playhead to a specific point in time, either Ctrl-click or Shift-click on the Playhead area on top. Make sure you don’t click in the main editing field in the middle of the screen as this won’t move the playhead, but will select a track instead.
Editing
When playing with the playhead you’ll have no doubt left-clicked and had a blue line appear instead of a red one: this is the Edit Head, and it’s used to select portions of audio from the Edit > Select menu. Leftclicking places the Edit Head – the beginning, and rightclicking places the Edit Tail – the end. These blue edit lines can also be dragged around, and middle-clicking places the two edit lines back together.
The blue editing lines can also be used to set up a loop. Select some audio between the two lines by clicking Edit > Select > Range, or right-clicking on a track and choosing Select > Range. Now press the blue Loop button on the main toolbar and the audio will loop between the blue lines next time you press Play.
Perhaps the most important feature in Qtractor is Split. This enables you to splice a track and do the kind of editing that makes using a DAW worthwhile over a simple wave editor.
First, select some audio and move the red playhead to where ever you want to splice it. Now from the main menu choose Clip > Split. The selected audio will now be chopped in two, and you can start moving things around independently of the remaining track.
Moving onto more detailed selection tools, depending on your version and screen size, you will either have a ‘Select clip’ button with a drop-down box, or three separate buttons: Clip, Range, and Rectangle.
Clip mode will grab whole chunks of track at once, whether that be the entire track itself or spliced portions. Range vertically selects audio from all the tracks at once – you’re grabbing a block of time rather than portions of a track. And lastly, Rectangle can choose portions of audio from one or more tracks with fine, delicate control.
Now for a really cool feature that we wanted to highlight. Rather than deleting chunks of audio, you can grab the edge of a track and simply drag it inwards. Nice so far. But guess what? You can also drag it back to ‘uncrop’ as it were, and even uncrop audio from recently pasted clips.
This interesting approach extends not only to cropping, but also creation. When you click and drag a
clip’s border, if you hold Ctrl, Qtractor will generate more of the same audio based on what has gone on before it. Though make sure that you have your BPM and time signature set correctly – then the Snap feature can break your music down into perfect bar-length chunks, which can be dragged around at will.
Music In
So far we’ve managed to avoid tricky connections in JACK, but we’ll need to start patching things together to record MIDI. Let’s start by getting a proper external MIDI keyboard going, which will be easiest if we just use a plugin within Qtractor.
First, create a new track. Follow the same steps for Add Track as before, but this time under the Track tab choose MIDI instead of Audio. Now click Add and search for a suitable synth plugin. Calf Fluidsynth is particularly popular and can load new soundfonts, though Yoshimi has its own sounds if you don’t have any soundfonts. Back in the Track window, make sure the light is enabled next to the plugin name (click it and it will go green) and then press OK.
To test your plugin, go the main menu and click Clip > New, which will open a piano roll editor similar to Rosegarden. Click the piano keys on the left to see if there’s a sound. If not, try another plugin.
Now plug in your actual MIDI keyboard and press the red Connections icon. On the panel to the left are your output ports, and on the right are your input ports. As long as you’re not running anything else, Qtractor should be the only client for the input ports. On the left however are multiple entries. By default there should be only two clients: Midi Through and Qtractor.
If your MIDI controller has been successfully detected there should now be a third entry in this list – in our case, our Korg keyboard was called microKEY. Choose your controller’s entry on the left, Qtractor on the right, and click the blue Connect button.
With any luck, pressing a key on your MIDI device will finally emit a glorious note from your PC. If not, go back and check your synth and plugin settings, and make sure your device is on the right channel.
If you don’t have an external MIDI keyboard, you can either draw out notes by hand in the piano roll editor, or you can use a virtual MIDI keyboard like jack-keyboard. If you choose the latter you’ll need to fire up the program externally, along with a synth program like ZynAddSubFX, amsynth, or Qsynth, and hook them all up to Qtractor in JACK.
Unfortunately jack-keyboard didn’t detect in the Connections window, so we used QjackCtl to attach everything externally. QjackCtl is made by the same developer as Qtractor, and the interface works essentially the same as Qtractor’s Connections window. To use amsynth in this example, press Connect in QjackCtl, and in the Connections window open the MIDI tab.
Now connect jack-keyboard on the left to amsynth on the right, and jack-keyboard to System in the same manner. This will sort out MIDI input, but to get Qtractor to play sound, open the ALSA tab and then connect Qtractor to amsynth.
This should hopefully get MIDI inputting to Qtractor as well as sound playing back with MIDI. However, you may still need to take the irritating extra step of choosing another channel under jack-keyboard from the Connected to menu – system:midi_playback_3, for example.
Expect crashes and having to redo JACK connections – this method is unreliable. Use a real keyboard if you can, and take a screenshot of your settings when you
get it to work! When you have MIDI working properly, the recording controls will work the same as with basic audio, and when you’re done recording, you can use the lovely piano roll editor.
On the buses
If you’re new to audio editing, buses are like a shared channel to which multiple tracks can connect and share a function. For example, perhaps you want to share a reverb plugin across multiple tracks to simulate a room effect. With buses, you can simply apply the effect to a bus and then attach as many tracks to it as you like.
This is where audio editing definitely becomes more advanced, but let’s do a very basic walkthrough using the reverb example. First, open the Buses window by going to the main menu and selecting View Buses. Now we need to create a bus with duplex audio, meaning it will both input and output audio.
From the left of the window click Master from under the Audio heading. In the Properties tab on the right, first give your bus a name other than Master – perhaps reverb-bus – and make sure the Mode is set to Duplex. Click Create now, or otherwise your plugin will end up on the Master channel.
Now to add your reverb, choose the Output Plugins tab on the right, click Add, and the Plugins window will appear. Enter reverb into the search field and pick whichever plugin takes your fancy and click OK. Make sure the light icon is turned on next to the plugin name in the Buses window.
That’s the bus created, but now you need to plug a track into it. Open the Mixer window and look for the blank space under your track’s name – this area will list all of your ‘inserts’ to come. Right-click in this empty field and choose Inserts > Audio > Add Aux Send.
This will open the Aux Send window. At the bottom of the window will be a menu Aux Send Bus, choose the reverb-bus entry and make sure to turn on the green light for Active in the top-right corner. Before you close this window take note of the Send Gain slider, as this will control how loud the effect will be.
All going well, your effect bus should now be running, and you can turn it on or off with the green light in the formerly blank area of each track.
Sounds good
Sometimes Qtractor can be a nightmare to setup and it can get crashy when presented with something unexpected. But it’s stable enough once you establish a working flow, and by using JACK’s agnostic approach to sound connection, you’re ultimately given more power to create new kinds of sound.
The interface is also much more inviting than something like Ardour, and will be a welcome approach to any intermediate users. Developer Rui Nuno Capela has created an endearing melange of all the major editors – a bit of Rosegarden here, some Ardour there, and a large helping of old ProTools slathered on some Cakewalk and Cubase. It’s a brilliant kind of mongrel that could only be bred by open source.