つつ・
つつ is the written ながら: one person does two things at once. After a verb of knowing or thinking, usually as つつも, it is "although": you knew better and did it anyway. つつある is a different thing, a change under way.
while doing
I put the report together while checking the materials.
although
I knew it was wrong, and I lied anyway.
How to form it
Verb ます-stem + つつ（も）
聞きます → 聞きつつ, します → しつつ. It follows verbs only.
Which つつ?
I sorted the documents while listening to music.
Two things going on together: while.
I thought it was pointless, and still I reread the old email again and again.
What I thought and what I did pull apart: although.
With も it is nearly always "although": the two halves pull against each other. Without it, look at what follows: if it goes against what the person knows or thinks, it is "although".
While doing: the written ながら
It works as ながら does: one person, and the main action comes last. The difference is where you meet it. つつ belongs to reports, essays and speeches, and to careful talk at work.
I noted down the differences in pronunciation while listening to the recording.
Written: an account of how you studied.
I noted down the differences in pronunciation while listening to the recording.
The same thing, as you would say it.
We will consider our future policy while listening closely to local people.
An official making a statement.
Let's move ahead little by little, seeing how things go for a while.
At work. 様子を見つつ is something people do say aloud.
Although: つつも
What someone knows, thinks or feels is one thing, and what they do is another. About yourself it is an admission, often ending in てしまう. About someone else it is often a criticism.
I knew I should apologize, but I couldn't bring myself to.
I kept thinking I must write back soon, and a week went by.
The person in charge knew there was a problem and still did not do enough about it.
知りながら says the same thing a little less stiffly. In conversation it is mostly ても or のに.
I know they are bad for me, but I can't give up sweet things.
In an essay.
I know they're bad for me, but I can't give up sweet things.
As you would say it. 分かっているのに works too.
Close neighbours
つつあるN2
With ある it is a different thing: a change under way, in news and reports.
The economy is gradually recovering.
ながら（も）N2
After a state: a verb like 知る, an adjective or a noun. You admit something that sits oddly with what follows. 残念ながら is this one.
Our home is small, but it's a happy one.
もののN2
The written けど: you grant a fact, then say it didn't lead where you'd expect. Bought, but not used.
I bought a new camera, but I haven't used it once yet.
にもかかわらずN2
The formal のに: a result that defies the circumstances, stated as fact. It goes straight onto a noun.
Despite the rain, a large crowd gathered.
Check yourself
1Which one is "although"?
Choose an answer to see why.
2Which sentence is right?
Choose an answer to see why.
More sentences
The person in charge narrowed things down to a final proposal while comparing the merits of each option.
As I reread my father's letter, I thought about the choice I had made back then.
They accepted that it was needed, but put off bringing it in for budget reasons.
Uneasy as they were, they went on with the negotiations.
I know it's bad for my health, but whenever a deadline is near I end up staying up all night again and again.