If you’ve ever had a great idea in your head, but the moment you start speaking, your words come out stiff, rushed, or uncertain, this is for you.
I’m Tim Lu, and I built Rehearso Lab because I’ve lived that exact feeling.
The “second-language” problem nobody talks about clearly enough
Speaking a second language is rarely just about vocabulary. It’s actually about the subtle things: timing, tone, rhythm, and knowing exactly when to pause. It’s about sounding like you, rather than a translated version of yourself.
The hardest part is that the pressure makes everything worse. In a normal conversation over coffee, you can recover from a mistake. You can laugh or restart a sentence.
But in a presentation or an interview, it feels different. The room gets quiet, the stakes feel high, and you start thinking about how you sound instead of what you mean. That little bit of insecurity quickly turns into a feedback loop. You worry that you don't sound natural, or that people can tell you're nervous, so you speed up to get it over with. Suddenly, you aren't fully present anymore.
My old, very “manual” way to practice
Before Rehearso Lab existed, I relied on a method that honestly works, but is incredibly painful.
I would record myself speaking, listen back to catch the parts that sounded unnatural, and then repeat the process. I’d do this over and over again until it finally felt like “me.” While it’s effective, it takes a lot of time, and it’s hard to know what “good” sounds like when you don’t have a consistent reference to compare against.
Also, let’s be real: listening to your own voice on repeat is not exactly a fun way to spend an afternoon.
Then the AI era arrived (and something clicked) When voice AI started becoming real, especially voice cloning, I realized something. I wondered if I could practice by “reading after” my own voice.
I realized that if I could generate a clean, natural reference audio in my own voice, my practice could become much more structured. It turns out, this isn't just a hack. It’s a digital evolution of the Shadowing Technique, a method researchers have long known improves pronunciation and prosody. By pairing this with a structured Listen and Repeat loop, you stop guessing and start building genuine fluency.
Rehearso Lab began as a personal tool At first, this wasn’t a “startup idea” or even a public product. It was just me trying to solve a real problem in my own life.
I simply wanted to sound natural when speaking a second language, especially in interviews and presentations, without spending endless hours doing trial and error. So, I built a workflow where I could paste my script, generate high quality reference speech, and actually feel my confidence go up as I practiced along with it.
I kept polishing it, optimizing it, and making it smoother until it became a tool I genuinely wished I had years ago.
Why this matters now
We’re living in a time where self improvement can be easier than ever if we use AI the right way. I don't see AI as a replacement for learning or a shortcut that makes you less capable. I see it as a practice partner that makes consistency easier.
That’s what Rehearso Lab is meant to be: a way to rehearse your voice with structure so your ideas can finally come through clearly.
Who I built this for
I built this for anyone who speaks a second language and still feels nervous when the stakes are high. If you struggle with sounding “natural” under pressure, or if you just want a more efficient way to prepare, this is for you.
I know what it’s like to have the right thoughts but not the right delivery yet. I also know that with the right practice loop, it gets better faster than you expect.
I’m genuinely happy it’s finally online Rehearso Lab started as my personal tool, but now it’s online and ready to help more people. It is specifically for anyone still struggling with a second language while trying to show up confidently in interviews, presentations, and big moments.
If that’s you: welcome. I’m really glad you’re here.