AirVox ($3): Gesture-based controls offer exciting possibilities for music apps, as you can tell from our round-up of apps that make listening while driving safer. AirVox takes a different approach, enabling gesture-based music creation without ever touching your screen. AirVox does this by recognizing motions and hand gestures via the front facing camera on your iPhone 4 and translating these movements into musical notes and tones, making you the instrument.

Moving your right hand up and down controls pitch, while side-to-side motion with your left hand controls the volume. It’s sort of like a theremin, and it’s no mere toy — the app’s sound engine builds 48 presets from numerous selectable waveforms, with filters, oscillators and effects all individually adjustable to create and save your own custom sounds. You can share your masterpieces via email, WiFi, Facebook, and Twitter, once you upload from the app into SoundCloud.

Yesterday USA – Old Time Radio (free; pictured above): Whether you’re an old-timer reminiscing or a youngster with romantic notions of American radio’s golden era, Yesterday USA’s rebroadcasts of classic radio shows from the ’20s to ’50s will take you back in time. The app streams 24/7, with hours of public domain radio programs prepared and submitted by volunteers, as well as live broadcasts and special programs assembled by Yesterday USA staff. Streams rotate on a two-week cycle, so tuning in always leads to something new and surprising — or, perhaps more accurately, something between 60 and 90 years old that you probably haven’t heard before. Variety is the spice of… oh, you know.

iSheet Music (free): Attention session musicians, Suzuki Method students, and other sheet music devotees: the iSheet Music iOS app keeps your scores ready for when you need them on your iPhone, iPod Touch or iPad — and without the heavy binder, no less. This app organizes scores by artist, composer, and genre, eliminating unproductive breaks in your practice time when you would otherwise be rifling through loose pages and unwieldy volumes. You can download new sheet music within the app (prices vary), so your favorite artists and composers can all be at your disposal. Neat add-ons include an Audible and Visual Metronome to keep you in time and guitar chord diagrams to help with tricky fingerings.

Pixies Official (free): Avid followers of legendary indie rockers (the) Pixies will be amazed to know that the band recently released an official fan app for the iPhone. Stand-out features include a store with access to Pixies merchandise and tracks from the band’s complete studio catalog; a large archive of past live performances including free music; and a Four Square add-on that encourages fans to prove their dedication with badges, advancing their rankings on the leaderboard.

The app integrates with Facebook and Twitter and also links to the Pixies’ own social network where you can create a profile and interact with fans of the band from all around the world. There’s plenty of free music too. In addition to streaming notable live sets like Manchester 1988, 2004′s reunion show at the Fine Line Cafe, and the band’s acoustic performance at 2006 Newport Folk Festival show, app users can also download The Pixies’ entire 2004 Coachella performance.

MusicPound (free): Looking to compare libraries with a friend to see just how musically compatible you really are? MusicPound enables exactly that with an instant side by side comparison of your iTunes catalogs. A “Musical Score” keeps track of the completeness of your library and rates it on a scale from Groupie to Mogul, with the option to purchase tracks directly from iTunes to settle any discrepancies. Those not grandfathered in with unlimited data plans will be happy to know that linking two devices for comparison requires only Bluetooth connection, so using the app won’t eat up your data allotment by grabbing music over the air.

Ringtone Maker (free): We know, we know, there are too many poor-quality ringtone generators out there, and it tends to be the paid ones that have more mettle. Ringtone Maker might just be the exception to that rule. The app lets you create an unlimited number of ringtones from any song in their iTunes collection, or your own voice (or any other ambient sound). You can adjust the start time and length of your recordings with fade-in/fade-out; the speed; and the pitch of your recordings too. And all it costs is time.

Bandcamper (free): Many upstart bands take advantage of the popular service Bandcamp to sell music and merchandise. The site generally leaves it to independent developers to put this stuff into mobile apps; Bandcamper offers a great way for fans to discover artists on Bandcamp from iOS. Fans can stream music from artists’ Bandcamp pages even while not actively using the app; thanks to multitasking support, it keeps playing when the screen is locked, and can be controlled via headphone remote or iOS’s multitasking bar. You can browse artists by location and/or genre, or view top-selling artists. Any of this can be saved to your favorites list so you can go back and listen to it whenever you want.

LyricWiki (free): LyricWiki, a popular community-generated lyrics site, now has its official app for looking up lyrics on the go. The app auto-completes your search queries to make it easier to find the song you’re looking for, and lyrics are organized by artist and album for quick browsing of over 1.5 million songs, which the community has peer-evaluated for accuracy for as many as five years. The app and mother-site pay royalties to artists and publishers for all of these lyrics, so you can be sure that your favorite artist is being fairly compensated.

Coverjam (free): Whether you’re a superfan who simply can’t bear to listen to a favorite artist without seeing their face, or simply the type that enjoys a visual addition to your music, this app is for you. Coverjam displays amazing, high-quality photos of the artist that you’re listening to as you listen by scouring photo sites such as Flickr and Instagram to deliver everything from publicity photos to action shots, for you to enjoy on your lonesome or share via Facebook, Twitter, or email. You can play your music within Apple’s iPod app or Coverjam and see this slideshow either way. If you come across a photo that you don’t like, you can ban it so it’s never shown to you again.

Google Android:

UberMusic ($3.50): One of the hottest new releases for Android has to be this highly-customizable, fully-skin-able music player. UberMusic (no umlaut required) offers a thoughtfully-designed, highly-customizable interface; six widget options of varying size; wallpaper created from your album art; and scrobbling support through the Last.fm app, ScrobbleDroid, or Simple Last.fm Scrobbler.

We Are Hunted (free): The recently updated We Are Hunted app makes it easy to discover hot new artists every day. The app charts the most listened-to and buzzed-about music by tracking social networks and popular music blogs, and offers an updated list of hot songs and artists each day, so it never gets stale. Plus, it looks good, and you can stream full versions of the tracks. (Note: Hunted Media uses playlist technology from The Echo Nest, publisher of Evolver.fm.)

Guitar Hero 5 ($8, but sometimes free): Guitar Hero 5 was featured as the Amazon app store’s free paid app of the day a few days ago, but our editor was busy catching up after a sort-of-vacation… sorry! Most are probably familiar with the console game by the same name. This Android version offers similar gameplay, minus the plastic instruments, with 20 songs in three difficulty levels available in practice or career mode. Buff up on your virtual guitar skills even in the few miserable hours spent away from your television. We kid, we kid.

Neutron Music Player ($5): This music player has been climbing the ranks on the Amazon app store since its latest update, becoming the top paid, new app available there. Neutron Music Player, an advanced music player, was designed with audiophiles in mind, with a real-time 44-band (!) spectrum analyzer, wake timer, sleep timer, clock mode, album art, and another night interface option (in addition to the native Android one) to minimize eyestrain in low light. It also brings gapless playback and support for a wide range of audio formats (MP1, MP2, MP3, WAV, FLAC, AU and OGG).

Web Apps:

Ok Go x Pilobolus “All Is Not Lost”: Though not an app in the traditional sense, Ok Go’s web video thing is a pretty cool pseudo-musical use of your browser’s new-found HTML5 capabilities (providing that browser is Google Chrome; the video won’t work on anything else.) The site combines the latest music video from the indie-rock group that has become famous for such things, along with the stylings of modern dance company Pilobolus.The result is an interactive dance-based video that spells out messages from inputted text — another neat trick from these tricksters.

Check out the entire This Week in Music Apps series for more download ideas.