Converting audio to midi (which can then be converted to score) is a very difficult programming problem which people have been working on for decades - and with very limited success. The crude basics are simple enough - you mathematically analyze the audio and figure out which frequencies are in the source. But it’s the details which are immensely complicated - how do you determine which is the fundamental note vs. the overtones/harmonics - how to handle even the slightest shifts in tempo, etc, etc, etc,
I’ve recently been mucking around with two different “audio to midi” applications - Melodyne & Widi - with rather limited success. Both advertise the ability to handle polyphonic material. I my experiments, Melodyne did a somewhat crude transcription of a piano piece - but it needed a lot of work before it could be made accurate. Widi’s conversion was completely nonsensical - but maybe I was doing something wrong.
That said, you can download a 30 day trial version of Melodyne, and you can buy a 30 day trial version of Widi for $30 US.