The strengthening seems a little extreme if you are just boarding out the loft for a music room, we would suggest engineered timber products rather than steelwork.
Also, if you are just wishing to have limited access i.e. just to get into the space we would suggest a loft ladder access would suffice.
We would then question why you would need to make the loft hatch larger.
Jeremy Wedge MIstrutE CEng on behalf of Loft Conversion UK
