Despite the early frustrations with Rosegarden, I’ve actually made some significant progress. By reading the great but simple tutorial on UbuntuStudio on how to set up things like JACK in Ubuntu, I am now able to use Rosegarden with the included synth plugins to actually play .wav samples and sequence it to resemble something that a some people would call music. In other words, I’ve actually managed to do pretty much the same thing I used to do on my real synth (a Roland W-30). I recorded some of the samples of an old song I wrote ten years ago on the W-30, and sequenced them using similar sound effects (mostly reverbs and delays).
However, I’m sure there are easier ways of doing it, because I’m forced to use separate MIDI tracks (and synth plugins) for every sample .wav file I’m using. On the W-30, I could load several samples and assign them to different keys on the keyboard. Don’t know how that stuff works in Rosegarden. Also, I have yet to figure out how how to e.g. control the plugins through the sequencer (for example, dynamically change the cutoff frequency of a low-pass filter plugin), so everything is pretty static. In other words, the filter doesn’t change over time during playback, unless I do it manually while the song is playing. On the W-30, I could control the filter slope through MIDI instructions. If you’ve ever attempted to create techno/trance music, you know how important filters are. There’s hardly any song not making extensive use of them, or any other dynamic effect for that matter.
Anyway, I’d like to say thanks to the author of UbuntuStudio. If it wasn’t for the tutorials on that site, I would probably have given up and installed Reason instead.