Mecha anime from childhood

[Sunspray]

Hello everyone,
This is my first post so please do not be harsh on me

I'm badly looking for an anime from the past, I've searched many places without any result, maybe you can help me. I'll try to list everything I remember.

1. It was some kind of mecha anime
2. Main protagonist was taken and locked in prison
3. In the same building there was huge mecha that some scientist tried to wake up but without success (mecha was sentient)
4. There was an attack during which this mecha woke up and recognized protagonist prisoner as his pilot
5. There were some infected people and infested planet
6. There were 2 animalistic mecha summoned with flute that helped main protagonist (flute ended in some antagonist hands and went hostile)

I've spent many years looking for this and I really appreciate for any help.

Have a great day!
Sunspray

[Seto Kaiba]

Can you give us a directional estimate of how long ago you saw the series in question?

[Sunspray]

It was approx. 20 years ago

[Mafty]

After doing some research on forums it may be Yamato Takeru. It's a fairly obscure series that aired on Saturday evenings in 1994, and a number of people remember watching it as kids. The main character is imprisoned in a cage by the Village Elders in the first episode for his rambunctious behavior, then later is summoned into the Susanowo robot when the aliens arrive, he also can apparently summon the robot with not a Flute but an Ocarina, also they are apparently living with aliens on another planet after leaving Earth. I can't really find more information than that, but hopefully this helps.

[MythSearcher]

After doing some research on forums it may be Yamato Takeru. It's a fairly obscure series that aired on Saturday evenings in 1994, and a number of people remember watching it as kids. The main character is imprisoned in a cage by the Village Elders in the first episode for his rambunctious behavior, then later is summoned into the Susanowo robot when the aliens arrive, he also can apparently summon the robot with not a Flute but an Ocarina, also they are apparently living with aliens on another planet after leaving Earth. I can't really find more information than that, but hopefully this helps.

Watched that back in the 90's on TV but still can't remember what it was about even after reading the Japanese Wikipedia page. Can't even remember if it was a good show or not, didn't leave much of an impression.