Have you checked the music threads in General Resources? There are literally hundreds of instrumental tracks in there, and all are free. There are also many instrumental packs in the web store here.
Or if you mean as in tiles then you need to mention which maker you're using...i.e. I know MV has a piano and an organ in the RTP tilesets and Comshou has some other styles, I also vaguely remember seeing someone who had guitars somewhere on an external site (can't remember which one) if you're after MV. I don't know about VX/Ace though as I don't have those.
EDIT: I just found some by Flaming Teddy Productions: Pretty sure they're VX. https://www.deviantart.com/hydrasis/art/Music-Room-452991174. The TOU are under the picture.
I just tested resizing the tiles from the link I put above with the VX tiles: https://www.deviantart.com/hydrasis/art/Music-Room-452991174 and they still look ok at 1:1 ratio to me but you would need to decide for yourself. There are violins and a violin case in there and the TOU do not prohibit use in MV. The tiles are free for use commercially or non-commercially you just need to give credit to "Quizical gin" or "Flaming Teddy Productions".
Since I‘m using a massive amount of the resources posted here in my game, I decided that anything made for it by me would be released in turn. Now that I’m close enough to finish a version of the game and not see them in use before I get my own out, and since it is Christmas, I decided to go...
Is there anyone who would like to resize some of sprites I've got and put them into MV sheet? I'm bad at that kind of things. I want to make a game, but I lack in resources and I'm bad at recolouring them, so my only option was to use a sprite maker from one game (Ive got permission to use it) but these are sprites from VX Ace and I only have MV. So, is there anyone interested in helping me?