I am a SuperCollider fan, too. For me it's the sweet spot between a modern programming language and a deep and performant synthesis/sequencing platform. SonicPi is perfect if you wan to start making music immediately, but consider that underneath is just another language interface for the supercollider synth server, so at some point you will want to go full SC, that is dialect of Smalltalk with some functional ideas. CSound is the oldest/most powerful/most frustating of the bunch, but at the core is composed of two parts: a description of the sound generators/effects graph and a list of notes/events. If you enjoy coding in assembly, CSound will be fun. Chuck has a very nice sync model (SonicPi is similar), but the language is very imperative, not my favourite.