Depends what format you have it in now. 160kbps opus is transparent for almost all music. That's 1/5 the space of a FLAC collection, or 1/2 the size of 320kbps mp3, two other popular ways to store music without noticeable loss in quality.
I actually do encode to 128 opus and crank up the encoder settings for music synced to my own devices, because I know they can play it. It's pretty much transparent to me but I am not an audiophile with audiophile equipment, which is why I keep the originals.
