Ohk so i have not heard anyone speaking of this problem
i load my usb with my live instruments and vintage synths
after that i load one of the files and use it so for instance i load vintage synth file
but when itry to load the other file which is live instruments it replaces the first file that a loaded
and i find that very foolish because it happens that some of the sounds that i like or would use on a gig
are on the other file and i want all of the sounds to be used but i cant
because the file that i load on to the mx keeps replacing thee first one i loaded and it sucks:( 🙁 🙁 please if someone can assist please do thanks in advanced

Welcome to Yamaha Synth and thanks for the question.

The MX loads “all” the Performances from a .X5A file, when you set the File “Type” = All
However, if you change the “Type” = Performance, you can then select a Source Performance (one contained in the .X5A File) and then set Destination Performance (the Internal memory slot to be over written).

Load the file with the most ‘keeper’ data, then select and load individual Performances from the other file library.
See page 62 of the MX49/61/88 Reference Manual.