Unable to get same result from FileSaver/Blob versus Node's fs - node.js

Question

I'm trying to generate a midi file (with jsmidgen) and I'm able to output it with node this way :
fs.writeFileSync('test.mid', file.toBytes(), 'binary');
That midi file is working perfectly. Then I'm trying to generate it from a browser and I download it with FileSaver.js this way :
let blob = new Blob([file.toBytes()], {type: "audio/midi"});
saveAs(blob, "test.mid");
That midi file is corrupted. I tried various blob content types without success and I've also validated that the file.toBytes() output is the same in both circumstances. I compared both hex outputs it looks like an encoding issue but I'm not able to find how to fix this.
Hex code from the good file (save in Node with fs)
4d 54 68 64 00 00 00 06
00 00 00 01 00 80 4d 54
72 6b 00 00 00 5e 00 90
3c 5a 40 80 3c 5a 00 90
3e 5a 40 80 3e 5a 00 90
40 5a 40 80 40 5a 00 90
41 5a 40 80 41 5a 00 90
43 5a 40 80 43 5a 00 90
45 5a 40 80 45 5a 00 90
47 5a 40 80 47 5a 00 90
48 5a 40 80 48 5a 81 00
90 3c 5a 00 90 40 5a 00
90 43 5a 81 00 80 3c 5a
00 80 40 5a 00 80 43 5a
00 ff 2f 00
Hex code from the bad file (FileSaver/Blob) :
4d 54 68 64 00 00 00 06
00 00 00 01 00 c2 80 4d
54 72 6b 00 00 00 44 00
c2 90 3c 5a 40 c2 80 3c
5a 00 c2 90 3e 5a 40 c2
80 3e 5a 00 c2 90 40 5a
40 c2 80 40 5a 00 c2 90
41 5a 40 c2 80 41 5a 00
c2 90 43 5a 40 c2 80 43
5a 00 c2 90 45 5a 40 c2
80 45 5a 00 c2 90 47 5a
40 c2 80 47 5a 00 c2 90
48 5a 40 c2 80 48 5a 00
c3 bf 2f 00
Is there something wrong with the way I'm using Blob or could I try another approach?
The code I used to generate the midi file is the first example on the jsmidgen page, the one playing a C major scale.

Answer 1

Do you need to use Blob specifically? If not, then you can use btoa.
I use jsmidgen as a primary dependency for my module(which acts as a wrapper and does some other things) and I faced a similar issue hence came up with this:
const bytes = file.toBytes();
const b64 = btoa(bytes);
const uri = 'data:audio/midi;base64,' + b64;
const link=document.createElement('a');
link.href=uri;
link.download = 'music.mid';
link.click(); // this will start a download of the MIDI byte string
I ve documented this in the context of my module with a working JS Bin in there too: https://scribbletune.com/documentation/core/midi