Looking more at the list Bryant tried, his video, a video from PunishingWaterfalls, and testing it myself, I don't like it. It mulligans so much more and has a higher chance of "do nothing" draw 7s (off Echo or Relay). There are several fizzles where you can't do anything after the Echo or Relay, passing many turns and trying to rebuild. Brain Freeze sometimes fails as a wincon. Access to colored mana is a bit unstable, leading to losses to mana denial & especially Null Rod/Ouphe. Mana stability improves a lot with the Brainstorm + fetch configuration. The build also has less protection, so it relies on things like all-in Narset + Echo hoping opponent has no interaction or misplays into Narset.

One design choice I don't like in many Song brews is playing too many 0s, at the cost of space for other things. At first glance that seems necessary to not fizzle with Song, but it also leads to worse mulligans, Echos and Relays. In all my brewing and testing with the deck since Song was printed, I think it needs a fine balance between action and "free" stuff. Going too far in either direction damages consistency.

The solution above is to have Saga & Narset as a fair backup plan when the "combo" side fails. But that's not necessary if the combo side is better tuned. Saga's a good fair backup plan but pretty bad in the combo lines as a colorless source and disappearing mana. Saga's also mana hungry, while the deck is mana-light. You're often forced to choose between making constructs or threatening storm lines, unable to do both at once due to the mana constraints. Overall I'm not impressed with Narset. It's strong if opponent misplays into it or if you have to rely on Echo + slow win. But it costs a lot of mana to dig, making it inefficient in the storm combo lines. With disappearing mana sources you really want 3 mana to draw 7 (Echo, Relay), not draw 2 over 2 turns.

After more testing I cut Narset and put Gamble back

//Lands: 12
3 Misty Rainforest
3 Scalding Tarn
2 Tropical Island
2 Volcanic Island
1 Taiga
1 Island

//Artifacts: 20
4 Lotus Petal
4 Lion's Eye Diamond
4 Chrome Mox
4 Mox Opal
1 Jeweled Amulet
3 Defense Grid

//Spells: 24
4 Brainstorm
4 Veil of Summer
4 Gamble
3 Repeal
3 Burning Wish
3 Galvanic Relay
3 Echo of Eons

//Enchantments: 4
4 Song of Creation

//Sideboard: 15
1 Echo of Eons
1 Galvanic Relay
1 Tendrils of Agony
1 Empty the Warrens
1 Reverent Silence
1 By Force
1 Pyroclasm
1 Consign // Oblivion
1 Brazen Borrower
1 Engineered Explosives
1 Tormod's Crypt
2 Surgical Extraction
2 Flusterstorm


Gamble has many uses:
- It sets up LED+Echo very reliably, letting you chain multiple Echos in a turn to storm off while Veil is still up.
- It finds SB answers when you need them (with ~80% success, which is better than digging with Ponder or Narset)
- It finds Burning Wish while you're going off, so you don't actually have to draw the whole deck with Song or Echo
- If you have a business card in exile with Relay, it can find mana (with 50-80% consistency, again better than digging with Ponder or Narset) and without risking discarding the business card

Most slots are self-explanatory.
Flusterstorm is there for combo mirrors (board out Grid & board in Fluster + Surgical to disrupt) or to help protect the combo against heavy spell hate (board out Repeal, Fluster on own turn doesn't conflict with Grid).
Borrower is for permanent bounce and backup fair wincon without wasting a slot.