The 10 year old 30" monitor would be as good a music stand as a new 4k monitor. Bolting such a heavy monitor on the keyboard is made impossible by the use of springs to dampen it out & the top heavy standing keyboard stand. The lion kingdom has nearly settled on the top heavy, standing keyboard stand. All LCD's are still made of solid glass. Even dual ipads would unbalance it.
The largest light weight display is the $700 13" diagonal Sony DPT-RP1. Far cheaper than an ipad, but useless for any games. It's only use is reading PDF's.
Instead of a higher resolution display, there's also simplifying the music for a lower resolution display.
320x100 was once plenty of resolution for a line of music. Forget about cut & paste. The lion kingdom actually did painstakingly copy a short Dan Coates arrangement to Music Construction Set. With today's knowledge, it would have been faster just to write a better program. The C64's graphics features would have had an easy time supporting this kind of program.
Being able to notate music is a big wish for the music screen. Rather than combining a drag & drop interface & MIDI, it would almost be easier to use a keyboard & MIDI. Modern touch screens are more like keyboards than mouse interfaces.