Jacquire King demonstrates what happens when you remove the front panel of an upright piano and mic directly off the soundboard. The technique opens up the sound, adds harmonic richness, and brings you closer to the hammers for a more percussive, detailed attack.
With the panel off, there's less low-end buildup in the corners, which means you can spread the mics wider on the bass side without the muddiness you'd get in an enclosed position. The tradeoff is a slightly softer low-mid weight compared to miking with the panel on.
King also walks through how removing the panel changes the gain structure and compressor behavior. The frequency balance shifts enough that the compressor reacts differently, so settings that worked before need to be revisited. It's a good reminder that mic placement and signal processing decisions are linked, not separate.