I Made a midi player but midi has a lot of instruments that are not included like standard kit as shown in the url, also if you can add a xylophone and the others then I will be happy.
https://qsrdrums.com/webhelp-responsive/References/r_general_midi_drum_kit.html
A vibraphone is a type of xylophone.
Unfortunately, you can only add custom instruments by modifying the extension, and hosting the extension yourself. If you really want to do this, all the js files you need are in the snap source code in libraries/TuneScope/.
I actually have my own modification of the library that makes some improvements to the existing library (and some changes to the note duration system). If you want to look at how I made it, then you can go here.
Isn't there, like, a universal standard list of MIDI instruments? Does Tunescope not include them all because it'd take up too much memory?
There is a General MIDI standard, including a list of 128 instruments / sound effects, a separate list of 47 percussion instruments, and several extensions. So I imagine a selection was (or even had to be) made for the TuneScope library. Apparently Tunescope currently offers 32 instruments: 24 from the list of 128, and 8 different drums from the percussion-47.
Though I can’t check exactly how much memory current TuneScope consumes, from what I can tell it’s probably a few MBs - so I guess most systems could accommodate many more instruments. A nice new option would be for a user to add extra instruments, may be download the appropriate sound characteristics from wherever TuneScope got them. Depending on TuneScope’s software architecture such feature may either be easy or hard to implement.
tone.js supports all midi instuments if you look ate the instrumentMap.js file
They are both mallet instruments. A vibraphone has metal bars and it can have a long sustain with a vibrating effect. A xylophone has wooden bars and it has a sharp, quick sound.
Adding to that, in the General MIDI standard they are considered different instruments: vibraphone = #12, xylophone = #14 (and telephone: 125 
)
yep
and that's in the tone files in tunescope and thats why I don't understand why it does not use tones
Pretty sure Tone.js only includes some instruments, not all, most likely to not have gigantic file size. But it does have the ability to add any instrument.
it has a lot more including a kit standard
I know its not all but it is still a lot of them
It'd be nice if it had the full menu of instruments and downloaded the one you choose dynamically!