As far as I know, Venus controls voice and beauty, you can work with Venus for this:
Venus 1225
Regarding rhythm, and music, and I think this is also connected to intonation, the Raidho rune (number 5) is suitable for the purpose:
Futhark/Odin
To understand what the number of repetitions is:
The number for Raidho is five, so you would want to vibrate this rune for a number corresponding to five, such as fifty times for each session.
During the meditation, visualize the Raidho rune as you can. In time, when you open your mind, this can all be simultaneously. The rune should be shining with power.
Also, how planetary Squares (like that of Venus) work:
Magickal/Kabalistic Squares: How to Correctly Use These
Personally I have never tried this, in my life I have decided to apply myself in things other than singing, such as the study of logic, strategy, combat, investigations, persuasion, etc. so while I could tell you how effective Uruz is for athletic ability, I can't tell you how effective Raidho is for this type of artistry. BUT, may I remind you that I think that to make good songs you need your songs to also have good lyrics. I think the Ansuz Rune (number 4) is suitable for the purpose:
Futhark/Odin