midomiMidomi, a mobile application that lets you identify songs by singing into the phone, today became the No. 1 paid music application on the iPhone.

Tomorrow, the company will also announce it has raised $4 million in fresh venture capital funding, led by Walden Venture Capital’s Larry Marcus.

The application boasts several million downloads (the company isn’t specifying exactly how many). It launched the $4.99 application three months ago, and the company became profitable earlier this year.

Music recognition applications are pretty cool: Shazam, a popular free application, says it has gotten 35 million users and enjoys its lead partly because of its early start. The company has been around for a decade, and its free offering has certainly helped it maintain the edge. However, in order to identify a song, Shazam requires you to hold your phone up to a radio or other medium playing the song. Gracenote is another popular application that does something similar.

Midomi, built by a company called Melodis based in Silicon Valley (San Jose, Calif.), has built sophisticated technology that also lets you hum or sing a song yourself, giving you an extra easy way to find a tune that’s just ringing in your head but which you can’t remember the name of.

It identifies songs about three times as fast as Shazam (see the video below for comparison). It takes about five seconds and shows you results automatically. With Shazam, you press a button, which starts 12 to 15 seconds of recording, and then you have to wait another five seconds to get results.

Melodis continues to improve Midomi with new features: Before, it required you to first select whether you’re going to hum or hold the device up to a radio. Now, it detects what you’re trying to do automatically. It also has one of the best search-by-voice applications on the market — a free feature that lets you search for contacts on your iPhone using simply your voice.

Notably, it so happens that investor Walden VC’s Marcus was the first investor in music company Pandora, which is now the top free music app on the iPhone. Pandora, a 10-year-old company, struggled for a long time searching for investors, and Marcus took a risk on it. Pandora went on a very tough ride for years, but its popularity has recently exploded (it’s one of my favorite applications).

Melodis chief executive Keyvan Mohajer said Marcus’ expertise in the consumer web fills a need for the company, which has so far had backers known more for their engineering backgrounds. One of the company’s advantages is that it has built its own technology; most other music-recognition applications license their technology.

Mohajer said the company is doing well enough that it didn’t really need to raise a round, but he chose to do so to get Marcus’ help, and also to get backing from an unnamed major non-U.S. global device maker, which became a strategic investor in the round. We’re hearing the device maker is not Samsung, which already pays a royalty to Midomi to pre-load the app on its phones. The company previously raised $12 million from TransLink Capital, JAIC America and Global Catalyst Partners.

We wrote about Midomi when it first launched. The company’s first app for the iPhone, launched last year, was free, but that was merely a “proof-of-concept,” according to Mohajer. The company upgraded the user interface and started charging for the app three months ago.

Midomi also powers the mobile music search for Japan’s second largest carrier, KDDI, which claims to sell more songs than iTunes in Japan.