“We had a very long and powerful goodbye.”

“I will miss my friend forever,” she wrote on Instagram late Sunday.

With Tony, I got to live my life in a time warp.

Tony Bennett and Lady Gaga perform live at Radio City Music Hall

Tony Bennett and Lady Gaga perform at ‘One Last Time’ concert.Kevin Mazur/Getty Images for LN

Tony & I had this magical power.

She continued, “But it wasn’t an act.

Our relationship was very real.

‘Straight ahead,’ he’d say.

He was an optimist, he believed in quality work AND quality life.

Plus, there was the gratitude… Tony was always grateful.

Gaga went on to address Bennett’s struggle with Alzheimer’s.

“I’ve been grieving the loss of Tony for a long time.

We had a very long and powerful goodbye.

Though there were 5 decades between us, he was my friend.

My real true friend.

We were from two different stages in life entirely inspired.

Losing Tony to Alzheimer’s has been painful but it was also really beautiful.

An era of memory loss is such a sacred time in a person’s life.

There’s such a feeling of vulnerability and a desire to preserve dignity.

The pop icon concluded, “I’ll never forget this experience.

I’ll never forget Tony Bennett.

Don’t flinch when you feel sad, just keep going straight ahead, sadness is part of it.

Take care of your elders and I promise you will learn something special.

1 on theBillboard200, bridging the gap between Gaga’s younger pop fanbase and Bennett’s enduring audience.

“Because he’s not the old Tony anymore.

But when he sings, he’s the old Tony.”