I would think half of the tuition would be significant but it depends on the cost of the school.
Our state schools don't offer much at all for test scores but our state itself does. A 28 + will get you half off tuition only. Our state tuition is only about $6,500 a year so it is just over $3,000 with the scholarship. The state schools will throw in $1000 - $1500 more for 28 - 30 on the ACT but that is for the first year only.
The private schools DD has applied to are offering her $15,000 - $20,000 but those are $45,000 + schools. None of those schools offer that money for scores under 30 from what I can tell.
That has just been our experience with the schools DD has applied to or looked at. Obviously, all schools vary.
My one regret in life: Not pushing my kids into something musical. From everything I can tell, music scholarships are plentiful. You can minor in music and still pursue something else. I keep telling my 17 y/o that it might not be too late to pick up the oboe and have at it.