Hi reubenchng!
I usually go by hour. But in some cases it may result in a very expensive result and in that case I come up with a fixed price. But that depends on the client as well.
Lets say you have a client that you know changes his/her mind a lot or wants to change a lot of things a lot of times. In that case you could come up with a fixed price and then make a price for additional changes by hourly rate.
If I where to rent a studio I think its not a matter of getting discount if you rent it 5- 6 hours. more like 5 - 6 days. Just to set up for a recording takes more than an hour so 5 hours isn’t that much.
If you want to give a little extra to the customer you can name your hourly price and then drop that price per percent per hour so that the customer gets some extra value for each hour.
Oh just one thing that i have ben doing way to much is underprice my work. Don’t do that! It will just lead to you getting disappointed and the result being compromised. Feel ok with the price from the beginning. Its not worth working if you don’t get enough pay.
Thats my point of it 