Ubuntu – Virtual MIDI Piano Keyboard setup

First of all, VMPK does not pass MIDI data through it. That means that if you use it to play notes it will output them, but if you'll provide it with MIDI input it will highlight the pressed notes, but will not output them. To enable passing MIDI to the output, go to menu Edit->Connections, select "Enable MIDI Thru on MIDI output", and confirm by pressing OK. This will get your MIDI connection to work as on the picture you provided, and QSynth will recieve the MIDI input from your external controller.

I am not sure how did you set up QSynth, as it cannot be deducted from these screenshots you have provided (silly QSynth!). However, there are some things you should make sure to get it to work:

• Use a soundfont, as QSynth will not make any sound without some. Click on the 'Setup' button, then in tab Soundfonts use the Open button to select a sf2 file (if you don't have one, install package fluid-soundfont-gm or fluid-soundfont-gs, or look for them on the web, as thousands of soundfonts are available for free). After that change QSynth will ask you to restart it's engine, allow him to, by answering 'Yes'.
• Afterwards, make sure the ALSA connections are as they should be (QSynth will reset it's when restarting the engine). Also, remember to connect it's audio output to system output in JACK's audio connections window.

I hope it will help you. Ask in case of any further problems :)

If you just want to get your keyboard to play sound, this is very simple, and you won't need JACK nor Rosegarden for that. These tools are great if you want to record MIDI signal, write notes, and route audio between separate applications, but you don't need that to play sound with your keyborard.

My step-by-step would be to:

1. Plug in your MIDI device to your computer. If that's a USB MIDI keyboard, just plug the USB, if it has only MIDI plug, you may want to use a MIDI to USB device.

2. Download/Install a synthesizer. There is a large variety of sound synthesing applications for Ubuntu. You may like ZynAddSubFX (really powerful one), FluidSynth or QSynth (support soundfonts), AMSynth, AMS. Make sure to browse Ubuntu Software Center for synthesizer that will grab your interest.

3. Launch the synthesizer. Of course it has to be running to produce sound.

4. Tell the system to pass data from your keyboard to the synthesizer. You need to create a link between your keyboard and your synthesizer, so that MIDI signal is passed to it. You can either use aconnect tool, or one of it's graphical backends (which are simpler to use), like aconnectgui or kaconnect. While aconnect is installed by default, you can get the other two from Software Center. Once you connect your keyboard, and synthesizer, follow to the final step...

5. Press a key on your keyboard. You will hear some sound! If not, make sure if your system sound is not muted, and that our speakers are connected. Also, some synthesizers require you to choose an instrument before they produce any sound.

6. Fine tune your synthesizer settings. You will most likely not enjoy the initial sound of the synthesizer. In case of ZynAddSubFX, this will be a plain sine wave, boring! However, you can easily browse a great collection of timbres, and you can customize them fully. All synthesizers provide you lots of customisation, it's worth to spend some time choosing what you like most.

7. Proceed to play. Good luck and have fun!

I have also once written an article on general workflow for music production with external keyboard on Ubuntu, it should be useful in your case. Here's the link.