note: this is a draft. there are a couple of screenshot missing.
After seeing that in OS X it's possible to use SimpleSynth, I got curious and wanted to know if the same was possibly in GNU/Linux, turns up: Yes, it's very possible; no more LMMS to play melodies (great piece of software but beats the purpose of coding music).
In a Debian based distro, the packages needed are:
qjackctlorpatchageoraconnect(qjackctlandpatchageare graphical tools but the three of them are good for the job)vmpkqsynthfluidsynth