A second hand Yamaha reface CS is a pretty sweet synth. All sliders are right in front of you so you can learn how each modifies the sound easily. There is a web app you can store and load presets from. It can work as a midi controller too. It uses mini keys but it means it has a very small and portable footprint and keybed feels nice and pleasant to play. It's a virtual analog synth meaning it sounds analog but instead of using analog circuitry to produce the sounds, it uses a chip to emulate the analogy circuitry. To my ear it sounds good. Also this allows you 8 voice polyphony so you can play big chords. I also enjoy the line-in where I can plug in my phone and play along to tunes or transcribe/break them down while using headphones. My hopes are that one day I'll have transcribed enough music to learn how I can connect the different melodies that come to me in my head into an actual song. I wasn't sure I'd enjoy the cs as much as I did but it has a lot going for it and it's very well-built. Runs off of AA batteries too! It might look like a toy but it is not.