Sometimes you run across a Mac app that’s so well designed and executed you add it to your “gotta have” arsenal. Such is the case with Strophes (http://stroph.es/), a new lyrics app for Mac OS X Lion. It costs US$4.99 and is available exclusively through Apple’s Mac App Store in the Music category.

I listen to a lot of music — and I like to know the lyrics to songs. Strophes automatically downloads and displays the lyrics of the songs you’re listening to. It’s compatible with iTunes, Spotify, Rdio, Radium and, with a downloadable Safari extension, YouTube (more on that in a moment).

When you launch Strophes you’re presented a menu of iTunes, Rdio, Spotify, Radium or YouTube. Click the one you want and the app will launch. In other words, click on iTunes in the Strophes menu and iTunes opens.

Play a song and the lyrics appear in the Strophes window. There are controls to pause, fast forward and reverse through a song or your music library. You can even access Twitter and Facebook directly from Strophes.

In the top of the Strophes window, you can click on a search option. You can also click on a “people” icon and get info — such as biographies — on the artist/artists you’re listening to, based on data from Lastfm.

You can choose to show the lyrics in a variety of languages and three fonts (Helvetica, Noteworthy and Bradley Hand ITC TT). I’m partial to Noteworthy. You can also customize Strophes’ look by choosing among three themes: Cafe Royale (my favorite), Charcoal and Golden Twine.

With Strophes and the downloadable Safari extension previously mentioned, you can go to YouTube and listen to any music video. You’ll see an extra button for “lyrics.” Click it to open Strophes and read the song’s lyrics. At least that’s the theory.

Strophes never missed a beat (pun intended) when it came to finding lyrics while running iTunes. However, it had problems finding lyrics in YouTube. I tried various artists including T.T.L., the Black Keys, Maroon 5 and Justin Bieber. More than half the time, the lyrics were unable to be found.

On, the bright side, if for some reason the lyrics can’t be tracked down, you’ll get this cute message: “Ouch, it seems like we couldn’t find any matching lyrics.”

I wouldn’t recommend purchasing Strophes for use with YouTube. But it’s a great complementary app for iTunes.

Rating: 8 out of 10

— Dennis Sellers