Was formerly an uncommon at instant speed that just had the modal option of tapping one or the other for .

Compared to Exhaustion, I believe this is reasonable, even if Exhaustion may be something of an outdated example of power level.

Especially as someone who's only been playing for a few years, I like the focus on a spell heavy environment. Some of these cards seem like 'dur' they would be really good with storm. That's kind of cool, but I was also wondering: what are the tools to stop them?

If this was Instant speed it might do that well (like Mana Short). Of course, both are/would probably be used more often to protect the combo.

Something I've learned from Pauper is that Green and White have very few ways of interacting with Spells. Even at higher rarities, you basically get Silence. Anyway, looking at that, I was thinking of a color pie shift, something like: Instant, G (or W), tap all lands and empty all mana from target player's mana pool unless that player pays 3. I think it's acceptable in Green (or White) since it's sort of like a Fog effect; the power level is fairly low and it only stops players 1 turn. And such a card would make the most sense in a spell themed/heavy environment like this one.

If the question is "Should this be an instant", I don't think it needs to be. It does it's job well at Sorcery speed, though, I did think to myself that new players might miss what the point of tapping my opponent's lands are. You tap them, then move to combat, where that player's pool empties. From there you can attack into a no-trick combat, or cast your spells with no fear of Countermagic. Or maybe even follow up with a Mind Rot, now that you know your opponent is tapped out.

I do wonder if this should pull a bit from Mana Short's effect, though, to make it easier for the new players to get it. "Then empty that player's mana pool", I think, would make the card easier to understand.

Strangely, I do think this would be fair in white. White doesn't normally tap lands to get the Silence effect... but I don't see why not.

I do think the card is perhaps too strong right now, though I'm not sure how difficult Melody is too pull off. In bigger formats it will just be U or 2 life even. It seems like it should cost 2U at least, because this can be Exhaustion + Mana Short, even without the empty mana pool clause. And aggressive decks like Delver might run it just for the Sleep mode. The melody could also say - "permanents tapped this way don't untap during their controller's next untap step."