If you want to make music in game jams, you're going to have make your peace with "Chiptune". You have to put Chiptune in air quotes because, other than music nerds, people don't really know that Chiptune is music made on VERY specific sources (namely the ROMs or whatever used in old videogames). This is all a bit semantic I know, but if you game jam then folks are going to ask for Chiptune but they don't really MEAN Chiptune, they mean "old-timey sounding"*. 

This Combinator does "Chiptune", it's actually a blend of subtractive synths and a sampled Farfisa organ but it does the tune well enough. I've used it in a few games now and always with an enthusiastic response. So if you have Reason 10 and download this Combinator, when they ask you "Can you do Chiptune?" you can say "Yes." with confidence.

* Allow me to drop a little science (just a wee bit) on you. The original chiptune producing chips were basically a kind of synthesizer known as a "Subtractive Synthesizer" which is basically a noise generator with a filter. A musician uses the filter to produce unique sounds, so you "subtract" noise until you find the pitch, timbre, sonority or whatever it is you're looking for. For reference listen to like ANY hit song from 1978 to about 1992 (and a lot of music today too). This Combinator blends two subtractive synths (one with a lot of the portamento "moving" quality of old video game music) and the Farfisa.  Combinator controls basically let you dial in more or less organ and more or less portamento.