LMMS, or Linux MultiMedia studio, is a free beta software that is being developed as a free alternate to FL Studio (it's called Linux MultiMedia Studio, but there is a Windows version). It is still quite in beta, but I find it extremely useful for making music. I'll let you guys decide but I'd definitely love to have a portable version of this. It leaves no registry keys, and only one configuration file.
Link: http://lmms.sourceforge.net/
License: GPL
Configuration files saved in .lmmsrc.xml in the user settings directory.
["bold"/"strong" tags fixed by mod Tim]
I searched and found this https://portableapps.com/node/18823 .
"It's just an online installer. It's not going to mug you.", JTH
"The shell is the key to unlock Linux's greatest advantages."