[REQ] Adjust speed in bpm instead of "times x"

[mozartix]

It would be great to have the opotunity to adusj the tempo of a song by its bpm value instead of just using the "times x" value.
as this has no reference it s quit chalanging to mach songs by this.
it also would be great to have the possability to save spesific values to the metadata like we can do with start- ans endtime