Understanding MIDI and soft-synths in Qtractor

[rothdu]

I've been experimenting with Qtractor using a midi controller and soft-synth plugins. There are a few things that I'm a bit confused about.

First, to describe my setup:

Midi controller: M-Audio Keystation 49 MK3. Connects to MIDI via USB. As far as I know, it outputs on MIDI channel 1 by default, this can be changed to other channels by tweaking settings on the keyboard.

DAW & connections: Qtractor (as explained). MIDI keyboard out routed to the Qtractor MIDI in.

Soft-synth: Surge XT. It seems to be available as a VST3, CLAP or LV2. I've created 2 MIDI tracks in Qtractor, and in each one I've "added" the synth as a plugin. I tried with both the VST3 and the CLAP.

A few things I'm confused about:

1. When adding a soft-synth plugin in Qtractor, there are 2 different places - the "plugins" tab where you "add" the plugin, and then the drop-down where you select an "instrument". What is the difference between these? What is the purpose of selecting the synth in the "instrument" dropdown after adding it as a "plugin" ?

2. Banks/patches can be selected from within the Qtractor track settings and also within the synth's actual gui. In my experimenting with Surge XT, the qtractor track settings section didn't have any descriptions (only patch numbers) and selecting patches that way seemed to have rather unpredictable results. Is this meant to be synced better? Can I just ignore the Qtractor settings and edit the synth settings in the plugin gui?

3. The Qtractor wiki seems to indicate that you have to select a different midi channel for every track, otherwise you'll be sending midi data to the synth along the same channels. In my experiments though, this didn't seem to be the case. Even with both tracks on the same channel, each track opened a separate instance of the Surge XT gui, which could be independently configured, and playing midi clips from the two tracks seemed to play the clips separately with the different sound configurations from each instance of the surge gui. Anyone have any explanation for what is actually happening here?

4. Qtractor wiki also said that you would have to configure midi on the channel which your controller inputs midi data, or select the "omni" button to receive data from all channels. In my experiments, I was able to record midi regardless of which channel I selected in the track, without the "omni" button selected, even thought my controller should only be sending data on channel 1. Is there something else I'm missing?

And some other questions about Surge XT specifically:

1. Is there any major difference VST3, LV2, and CLAP versions? And/or, why would I used one over the others? The only thing that I could see that was different was that qtractor flagged the VST3 as having 16 MIDI inputs and the CLAP and LV2 as only having 1.

2. I installed Surge XT myself using the package from the search website. Searching for plugins in Qtractor also revealed another one just called "Surge", which must have come installed with AVLinux. "Surge" was available as a VST2 or VST3. It seemed largely the same as the Surge XT plugin, but with some minor differences to the gui (e.g., different patch browser and settings menu). Is this just an outdated version?

Wow, that one was a mouthful. Thank you in advance for your help, fellow Linux Musicians

[Linuxmusician01]

Very interesting questions indeed. I hope that the developer of Qtractor, Rui Nuno Capela @rncbc who is active on this forum, will reply.

Regarding your 4 Qtractor questions:

Question 1. "Why is there a Track window to select an instrument plugin as well as a pull-down menu for an Instrument?"
The Instrument pull-down menu in the Track dialog window (double click on a track), I think, is to select a VST plugin (if you've got more than one on a track) and to set which preset/patch/bank it should use (if there is any). Sometimes you cannot do that in the GUI of the VST itself but only in this dialog Window. But Rui can give a decisive answer.

Question 3. "Selecting Midi Channels for Instruments and how they react to Midi Keyboard notes."
This, indeed, is confusing and may or may not be a quirk of Qtractor. Rui might supply us with decisive answer. I tried about 2,000 different settings with 2 VST's and Midi channels and sometimes one of 'm sounds, sometimes none. I tried it on 2 tracks, both on 1 track, 2 Midi channels channels etc., etc. Sometimes I see in Qtractor's mixer that it registers a Midi event, but no Audio output. No matter what Channel I set my keyboard to... Might have someting to do with the fact that you can also set a Midi Channel in (the GUI of) most VST's?

P.S. Want to see what your keyboard's Midi channel is? Open a terminal and use the command 'aseqdump'. Beware: it starts numbering at channel 0 and goes up to 15 (Qtractor names this Midi Channel 1 to 16!). Example for port 24, which is my Midi Keyboard:

Code: Select all

aseqdump -p 24

[rncbc]

hi, (shall answer qtractor related questions only:)

1. When adding a soft-synth plugin in Qtractor, there are 2 different places - the "plugins" tab where you "add" the plugin, and then the drop-down where you select an "instrument". What is the difference between these? What is the purpose of selecting the synth in the "instrument" dropdown after adding it as a "plugin" ?
2. Banks/patches can be selected from within the Qtractor track settings and also within the synth's actual gui. In my experimenting with Surge XT, the qtractor track settings section didn't have any descriptions (only patch numbers) and selecting patches that way seemed to have rather unpredictable results. Is this meant to be synced better? Can I just ignore the Qtractor settings and edit the synth settings in the plugin gui?

the "Instrument" drop-down on Track properties dialog serves to select proper bank and program (patch) names; it only works if the respective instrument definition is declared in "View > Instruments...", mainly referring to external/outboard MIDI instruments, not plugins; when a plugin is selected as instrument here, the patch, keys/notes and controller names will be only listed iif the plugin interface provides it and depends on the plugin implementation in particular and the plugin type in general: for instance, VST2 or 3 plugins (may) provide patch/program names, CLAP provides none atm. LV2 may (or not) provide the map through the MIDNAM interface if implemented on the plugin side, ofc.

to see some bank/program names you'll need to the select the plugin's name as instrument on the track properties dialog; depending whether the plugin interface provides those names, the bank and program listings should show them; idk. if Surge XT does it on either VST3 or LV2 types but quite sure the CLAP one doesn't.

1. The Qtractor wiki seems to indicate that you have to select a different midi channel for every track, otherwise you'll be sending midi data to the synth along the same channels. In my experiments though, this didn't seem to be the case. Even with both tracks on the same channel, each track opened a separate instance of the Surge XT gui, which could be independently configured, and playing midi clips from the two tracks seemed to play the clips separately with the different sound configurations from each instance of the surge gui. Anyone have any explanation for what is actually happening here?
2. Qtractor wiki also said that you would have to configure midi on the channel which your controller inputs midi data, or select the "omni" button to receive data from all channels. In my experiments, I was able to record midi regardless of which channel I selected in the track, without the "omni" button selected, even thought my controller should only be sending data on channel 1. Is there something else I'm missing?

you probably have Track > Auto Monitor on (as is the default): this way all incoming MIDI input is filtered to the current highlighted track's MIDI channel and through its plugin chain (ie. monitored) automagically; when Track > Auto Monitor is off, then each MIDI track will only accept incoming events to matching MIDI channels (or any, if "Omni" is on); to get those input events to play through the plugins, you'll need to turn "Monitor" on.

for plugin instruments that are inserted on tracks, the MIDI channel distinction is of no concern; it is however very important and quite mandatory for multi-timbral instrument plugins inserted on a MIDI output bus and ofc for external/outboard MIDI equipment.

Question 1. "Why is there a Track window to select an instrument plugin as well as a pull-down menu for an Instrument?"
The Instrument pull-down menu in the Track dialog window (double click on a track), I think, is to select a VST plugin (if you've got more than one on a track) and to set which preset/patch/bank it should use (if there is any). Sometimes you cannot do that in the GUI of the VST itself but only in this dialog Window. But Rui can give a decisive answer.

see above

Question 3. "Selecting Midi Channels for Instruments and how they react to Midi Keyboard notes."
This, indeed, is confusing and may or may not be a quirk of Qtractor. Rui might supply us with decisive answer. I tried about 2,000 different settings with 2 VST's and Midi channels and sometimes one of 'm sounds, sometimes none. I tried it on 2 tracks, both on 1 track, 2 Midi channels channels etc., etc. Sometimes I see in Qtractor's mixer that it registers a Midi event, but no Audio output. No matter what Channel I set my keyboard to... Might have someting to do with the fact that you can also set a Midi Channel in (the GUI of) most VST's?

if the plugin provides its own channel selector then, by all means, use it to match the MIDI track's channel, no matter if it's set to "Omni" (which only applies to recording and monitoring); all events that go through the plugin chain and/or output, are always transmitted on the designated MIDI track's channel.

hth.
cheers

[rothdu]

Thank you so much for the replies! Things are making a lot more sense now.

[Linuxmusician01]

@rncbc: Thanks! I understand it a bit better now.

I never heard of Qtractor's 'Midi Auto Monitor' function (F6) before today. When I set that off and I match all Midi channels (i.e. on 2 VST Synthesizers, my Midi keyboard and Qtractor's Track) then it works more or less as I would expected. I only hear one Synth at the time on Ch. 2 (example) when I press a note on my keybd. Not that I'd want two synths on one and the same track, but I tried this to get my head around Midi Channels.

However, when I switch in the Track properties window from one synth to another (or select the option "none") it becomes hard for me to predict which one I will hear. I'll try to explain w/ some screenshots.

In the screenie above the green LED light next to the 'Virtual Model Mini' VST (Minimoog) is lit (and said VST is set to listen to Midi Channel 2 just like my Midi keyboard). The selected Instrument in the Track Properties window is the 'ARP PE 2600 va' (ARP 2600 synthesizer). This is indicated in the screenie under the 'Instrument' column. Guess which one I hear when I press a key on the keyboard? Spoiler alert: it's the 'Virtual Model Mini'

In the screenie above both synths are selected, both are on Midi Ch. 2 and the 'Virtual Model Mini' is in the 'Instrument' column. Guess which one I hear (or both?) when I press a key? Spoiler alert: it's the 'ARP 2600' only. Same when I select "None" as Instrument.

Why is this?

P.S. I now also noticed that the number of Midi channel that a Track "listens to" is indicated next to the green LED light in the Mixer window (which lights up on a Note On and Off event). Very handy!

[rncbc]

Guess which one I hear (or both?) when I press a key? Spoiler alert: it's the 'ARP 2600' only. Same when I select "None" as Instrument.

Why is this?

you're chaining two MIDI synth plugins in the same column; unless the second one has pass-through audio in to out ports the output of the first one is just lost in the void, even though the MIDI signal reaches both instruments.

in those cases you should have only one plugin activated (green fake-led lit) and (all) the other(s) bypassed (fake-led is off), otherwise only the last one active in chain is heard.

ofc this applies to vast majority of instrument plugins out there but not to yours truly vee-ones, as these have the mentioned audio in-thru-out feature, and thus may well be inserted and active in tandem and then you may have, among other amenities besides unison, fake-layering, keyboard-splits, etc.

byee

ps. about the "Instrument" selection: to be clear, this setting has no effect to the sound being produced at all; it serves only to designate human-intelligible names to patches (banks, programs), note/keys and controllers; otherwise you'll see only numbers for patches and/or the default GM standard drum-note/key and controller names, as usual.

[Linuxmusician01]

@rncbc: Thanks for clearing that up. Again, I learned something today. Didn't know VST's need a 'pass-through' just like Midi (in - out - through). I take it that most - if not all - plugin effects (delay, flanger, etc.) have a 'pass through' so one can chain effects?

[rncbc]

@rncbc: Thanks for clearing that up. Again, I learned something today. Didn't know VST's need a 'pass-through' just like Midi (in - out - through). I take it that most - if not all - plugin effects (delay, flanger, etc.) have a 'pass through' so one can chain effects?

by design and definition, audio_fx plugins are all audio in-> fx -> audio out; instruments however are MIDI in -> synth -> audio out (quite often ther's no audio in whatsoever);

you may now see the difference
seeya

[Linuxmusician01]

@rncbc: Thanks for clearing that up. Again, I learned something today. Didn't know VST's need a 'pass-through' just like Midi (in - out - through). I take it that most - if not all - plugin effects (delay, flanger, etc.) have a 'pass through' so one can chain effects?

by design and definition, audio_fx plugins are all audio in-> fx -> audio out; instruments however are MIDI in -> synth -> audio out (quite often ther's no audio in whatsoever);

you may now see the difference
seeya

Aha. I see it now. There's a difference between audio-in/out and Midi-in/out. Thanks.