This thread tracks the commonly requested MIDI file output recording feature.
If you are also or only interested in recording to an actual audio file (WAV/MP3/OGG), see this separate thread.
If you upvote this, please share what usecase you have e.g. import into Ableton, Logic, etc.
Recording loops and being able to layer them would be nice too.
Would love to record what I put together.
It would be interesting if there was an internal recording / sequencer option using MIDI so you could record up to 1 or 2 tracks and play a 2nd / 3rd on top. This would make for some amazing complex pieces of music! I mostly use midi.city to test ideas for a few compositions or to play around in spare time. Thanks 
@howinteresting that’s exactly the direction that I’m heading towards. I’d like you to be able fully sketch out multi-track recordings using the MIDI standard, and then export into full-fledged DAW’s to master.
Being able to take the midi samples and create something more complex in a daw