You definitely don’t need a trigger for each and every note, but you will need a way to explicitly allow polyphony. I.e., you’ll need to decide the maximum amount of notes you’re okay with having playing at once, and then have that many sound sources.
There are a few ways to go about handling polyphony, but honestly the easiest one is probably to use multiple audio components, with the same MetaSound. When you make multiple instances of the same MetaSound, they don’t share parameters. So like, if you have two Audio Components each playing your MetaSound at ‘C’, and you switch the pitch of one of them to ‘A’, then you will hear both a note at ‘A’ and one at ‘C’. If you’re tracking Note Off in addition to Note On messages, it can get a little messy finding which note you want to turn off, but its definitely doable.
If you’re really determined to only have one Audio Component, you could also change the MetaSound to take an array of pitches and an array of velocities, respectively. You’d still need to have multiple voices within your MetaSound to play all of them, though.