I control Dovescape and Taigam, Ojutai Master, my opponent casts Martial Coup, I presume I could cast Swan Song in response to Dovescape's trigger, just so my opponent doesn't get all the bird tokens? (Since Taigam prevents my own instant/sorcery from being countered)
Both in Swan Song and Dovescape's ability, the token or tokens called for are still created (if possible), even if the spell in question can't be countered, since that action, in both cases, doesn't depend on whether that spell is countered this way. (For instance, Dovescape's ability doesn't say "...counter that spell. If you do, that player..." [C.R. 118.12].) See also this thread. (Note that if Swan Song's target is illegal, it will fail to resolve [C.R. 608.2b].)
Moreover, Dovescape's ability will get to resolve even if the spell it refers to was already countered or can't be countered, in which case when that ability resolves—
the instruction to counter that spell is ignored, because it's impossible (C.R. 101.3, 701.5a), and
that ability will refer to the spell's information or last known information, including its converted mana cost, to determine the number of tokens to create (C.R. 608.2h; see also C.R. 113.7a).
EDIT (June 7): Correctness edit.
EDIT (Aug. 4, 2019): Edited, including because some rules were renumbered with Core Set 2020.
EDIT (Feb. 24, 2021): One rule was renumbered in the meantime.
Both in Swan Song and Dovescape's ability, the player concerned creates the token or tokens called for, even if the spell in question can't be countered, since that action, in both cases, doesn't depend on whether that spell is countered this way. (For instance, Dovescape's ability doesn't say "...counter that spell. If you do, that player...")
So even if I cast Swan Song to counter Martial Coup ahead of time, Dovescape still triggers and create token for my opponent?
So even if I cast Swan Song to counter Martial Coup ahead of time, Dovescape still triggers and create token for my opponent?
Dovescape's ability triggers whenever a noncreature spell is cast, regardless of what that spell does or whether it can be countered. In this scenario, Martial Coup is a noncreature spell, so that ability triggers and goes on the stack above Martial Coup, before players get priority to cast other spells, including Swan Song (C.R. 601.2i, 117.5, 117.1a, 405.2). And if you cast Swan Song in response to Martial Coup, Dovescape's ability will likewise trigger, since it's a noncreature spell, and that ability will go on the stack above Swan Song (C.R. 405.2, 117.7). Then, in this scenario, assuming all players pass until the stack is empty (and that Taigam didn't attack this turn):
The Dovescape ability referring to Swan Song resolves, Swan Song isn't countered (since it's an instant spell you control), and you create one Bird token (C.R. 117.4, 608.2c, 101.2, 101.3, 701.5a, 202.3).
Swan Song resolves, Martial Coup is countered (since nothing says it can't be, here), and your opponent creates a Bird token.
The Dovescape ability referring to Martial Coup resolves, Martial Coup isn't countered (since it already was), and your opponent creates as many Bird tokens as Martial Coup's converted mana cost at the last moment Martial Coup was on the stack (C.R. 101.2, 101.3, 701.5a, 608.2h).
EDIT (Jan. 20): Clarification and correction.
EDIT (Apr. 6): Add rule citation.
EDIT (Aug. 8, 2019): Some rules were renumbered with Core Set 2020.
EDIT (Feb. 24, 2021): One rule was renumbered in the meantime.
EDIT (Nov. 27, 2021): Correctness edit.
So even if I cast Swan Song to counter Martial Coup ahead of time, Dovescape still triggers and create token for my opponent?
Dovescape's ability triggers whenever a noncreature spell is cast, regardless of what that spell does or whether it can be countered. In this scenario, Martial Coup is a noncreature spell, so that ability triggers and goes on the stack above Martial Coup, before players get priority to cast other spells, including Swan Song (C.R. 601.2i, 116.5, 116.1a, 405.2). And if you cast Swan Song in response to Martial Coup, Dovescape's ability will likewise trigger, since it's a noncreature spell, and that ability will go on the stack above Swan Song (C.R. 405.2, 116.7). Then, in this scenario, assuming all players pass until the stack is empty:
The Dovescape ability you control resolves, Swan Song isn't countered (since it's an instant spell you control), and you create one Bird token (C.R. 116.4, 608.2c, 101.2, 101.3, 701.5a).
Swan Song resolves, Martial Coup is countered (since nothing says it can't be here), and your opponent creates a Bird token.
The Dovescape ability your opponent controls resolves, Martial Coup isn't countered (since it already was), and your opponent creates as many Bird tokens as Martial Coup's converted mana cost (C.R. 101.2, 101.3, 701.5a).
Ouch, so I was wrong in that game. Guess I owe my opponent a win. Thx for the answer.
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs
Moreover, Dovescape's ability will get to resolve even if the spell it refers to was already countered or can't be countered, in which case when that ability resolves—
EDIT (June 7): Correctness edit.
EDIT (Aug. 4, 2019): Edited, including because some rules were renumbered with Core Set 2020.
EDIT (Feb. 24, 2021): One rule was renumbered in the meantime.
So even if I cast Swan Song to counter Martial Coup ahead of time, Dovescape still triggers and create token for my opponent?
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs
EDIT (Jan. 20): Clarification and correction.
EDIT (Apr. 6): Add rule citation.
EDIT (Aug. 8, 2019): Some rules were renumbered with Core Set 2020.
EDIT (Feb. 24, 2021): One rule was renumbered in the meantime.
EDIT (Nov. 27, 2021): Correctness edit.
Ouch, so I was wrong in that game. Guess I owe my opponent a win. Thx for the answer.
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs