So a question (that we've discussed a zillion times over) to revisit: can God still get the glory if we don't sound good? If we just all sing, and maybe sound a mess, no rehearsal, no perfection, no excellence, will He receive our gifts and be as pleased as He would be if we did it the "professional" way?
Here's the way I see it:
If we have a designated praise team and musicians, and there is a scheduled practice time. There should be absolutely no reason to come away with a product that is not polished. And, if a designated praise team with designated musicians with designated practice time(s) come together on a Sunday morning sounding a hot mess, ain't no way God is glorified in that, because the product shows where the heart is. If the praise team and musicians are willing to offer up just anything, they're no better than Nadab and Abihu (Aaron's sons who offered up strange fire). And we know how God felt concerning their offering.
Beyond that, the word says in Psalm 33:
"1 ¶ Rejoice in the LORD, O ye righteous: for praise is comely for the upright.
2 Praise the LORD with harp: sing unto him with the psaltery and an instrument of ten strings.
3 Sing unto him a new song; play skilfully with a loud noise."
It didn't only say "make a loud noise".
Having said that, when a group of people gather together, with hearts on fire for the Lord, and they sing songs of praise and can't one of them hold a note, it won't matter, because their heart is in their praise. And their love of God is shown in just the desire to give him praise.
Why is the 2nd example acceptable and the first not? Because, in the first example, the lack of effort to perfect the song through rehearsal shows their heart toward God. If you chose to be on the praise team, you are akin to the Levites whose job it was to minister unto the Lord. Ain't no half-steppin' when it's your "job".