Could you explain what you mean by mid tone selection masks to increase contrast selectively?
It was just an example of something you can do more effectively in PS than LR.
When dark shadows and bright highlights are already positioned correctly, possibly close to the edges of the histogram it is a way of increasing contrast whilst protecting these areas. I also use mid tone masks to increase saturation, when doing it globally would soon blow a colour channel out of gamut.
In the layers palette with a flattened image, or a base layer highlighted (not an adjustment layer) switch across to the channels tab.
Press cmd + click on the rgb channel. You have just selected the highlights.
Use the create alpha channel icon st the bottom (rectangle with a circle in it). A new channel is created, duplicate this process so you have 2 new channels the same.
Select the bottom one normally with a mouse click on the channel. Then press cmd + I. You have just inverted the highlight mask creating a shadow mask.
To select the mid tones we need to subtract the highlights from the shadows. This is achieved by ensuring the shadows channel is highlighted normally, then pressing cmd + a to select it all, then cmd + alt (should bring up a minus sign) + click on the fully selected shadows followed immediately without releasing the keys by moving up to the highlights and cmd + alt + click on the highlight channel.
When you release the keys PS will warn you about the small selection. Ignore it. As an exercise you can press the create alpha channel icon again to place that mask in the channels panel for future use, of you can just tab back to layers and click on curves adjustment layer. You will notice that it will load with the mid tone mask applied. Thus any adjustments you make are applied only to the mid tones with a perfectly feathered mask.
Advanced versions include intersecting the highlight and/or shadow masks to extend the midtone mask. Even the basic mask gives great flexibility within photoshop, because you can fade he opacity of the mask. Or instead if adding just a curved layer, once you have loaded the mid tones you can apply it to a group (which I think if as a folder) and put other adjustment layers within it, all with their own masks, gradients or colour channels etc.
This has taken ages I type on my phone but I can literally create and load a mid tones curve adjustment layer within seconds on a computer. Some people may ask why you don't just load curves and lock certain points off at the bottom and top, but I'm not sure it feathers the transitions the same, and is slightly slower, but has different advantages like eye dropping the points you wish to protect...