If you don't read music, why are you interested in getting the music into readable form? Why not simply use one of the many sequencer apps and share your music with others that way?
But if you really want to get it into readable form and you want to be able to play it in with a metronome, use a sequencer app (which will let you play it in real time), save as a midi file or musicXML file and import that into Notion. That way, you can edit what you play, in case you need to quantize the music so you don't end up with lots of 64th-note syncopations because you were not as metronomically precise as you thought you were, before trying to import into Notion.
Believe me, playing in real time into a notation program is not as easy as you think it might be because the app never knows if you were late or if you really want that 32nd note rest at the beginning of beat 1.
