You will need a hefty heat sink on your 7805 if that 5V is intended for powering the Beaglebone and Bela cape. Don't forget the thermal compound.
I think the BBB and Bela Cape take about 400 mA. (12-5)*0.4 = 2.8 Watts. Without a heat sink that's enough heat to exceed the 7805 maximum operating temp. 60C is uncomfortable to touch, 100C will burn you slowly (you can touch it long enough for your reflexes to jerk back) and 150C will burn you pretty fast. You should probably aim for 30C rise as this will keep it cool enough to touch -- heat sink + package thermal resistance should then be about 10C/Watt or better. Thermal resistance junction-case on this is 5C/Watt, so you need a heat sink with no more than 5C/Watt.
Fortunately the tab is GND so you can screw it directly to a 19" aluminum rack-mount chassis and the chassis will be sufficient to to keep the 7805 safe.
This is a good job for a switching power supply but you most certainly need a PCB with a really good layout to keep the noise out of the audio.
The 7805 is nice because you don't need to worry about switching noise, but you do need a good heat sink to handle the wasted power. If your 5V load gets up to 1A or more then you either need several parallel 7805's or consider SMPS.
As a point of reference, an aluminum chassis 19" wide x 1U high x 10" deep gets hot to touch at about 40 watts power converted to heat in the box. You could take about 4A into a 19" box at 12V and stay in a range that is probably safe to touch. I don't recall the temperature grade on the BBB to know how hot it can go, but cooler is always better.