Activate Cormela by paying ({1} magic symbol) and tapping it, adding ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) that can only be spent to cast instand and/or sorcery spells.
Cast Saw in Half by paying ({2} magic symbol) ({B} magic symbol) , destroying Cormela and creating two token copies of it with base power equal to half the destroyed creature's power and base toughness equal to half the destroyed creature's toughness, rounding up each time.
Put one of the Cormela tokens into your graveyard due to the legend rule.
The Cormela that died in step 3 and the Cormela that died in step 4 each trigger, returning Seething Song and Saw in Half from your graveyard to your hand.
Repeat.
If you have seven or more cards in your graveyard, this combo nets infinite mana.
Results
Infinite blue mana that can only be spent to cast instant and sorcery spells.