Notestar (free): Yamaha’s free iPad note-reader lets you automagically scroll through sheet music hands-free and play along with recorded accompaniment from professional instrumentalists and vocalists. As one might expect, a feature set like that doesn’t come totally for free. You can preview the sheet music and then purchase it within the app, at which point it downloads for easy reference.

Pixitracker ($2): We’ve reviewed some surprisingly robust music-making apps for the iPhone, but danger always lies in getting lost in too many fiddly knobs and controls. If that’s not your bag, Pixitracker might do the trick. It lets you quickly craft simple melodies and “chip tunes” with relatively little music knowledge. Despite its simplicity, this app includes a 16-bit sampler and pattern sequencer, MIDI, audio cut/paste, WiFi import/export, iTunes File Sharing, mic/line-in recording, and a variety of on-board sounds to work with.

iPeng ($10): This alternate controller for the Logitech Squeezebox allows you to manage playback on multiple Squeezeboxes — your music collection, internet radio, and unlimited music services like “Rhapsody and Napster” (someone had better tell them about Napster). You can play, edit, and save playlists on the fly, and access a variety of third-party Squeezbox plugins like AlienBBC, NPRMusic, AlbumReview and TrackStat to pack more functionality into your devices.

Deliradio (free; pictured left): Taking a cue from the locavore movement, this free streaming app sources radio playlists from artists who either live in your area or are set to perform there soon, using location data from your phone’s GPS. Helpfully, it includes links to their shows, so you can check out when and where they’re playing.

Octave ($5): This free, realtime spectrum analyzer for audio nerds shows output frequencies in 1/6th octave bands using time-domain analysis. The app claims to be built to ANSI specs, although you might face other performance limitations based on which iOS device you use. Still, it looks promising for audiophiles or anyone who works with live or studio sound.

Music Studio ($15): While its price might be steep (for the app world), those looking into full-featured studio recording for iOS would do well to check out the updated version of Music Studio. With too many features to list here, Music Studio crams in an 85-key position-configurable keyboard, 65 instruments (with 60 more available via in-app purchase), 100 drum loops, 8-track simultaneous CoreAudio support, audio copy/paste, a variety of import/export options, MIDI and waveform editing, and more.

The Sexy Sax Man ($1; pictured top-right): Nothing says sexy like a saxophone serenade. Some would say this is especially true if the man behind the horn is YouTube phenom Sergio Flores, with his mullet-to-end-all-mullets, black mustache rivaling that of Tom Selleck, essence-of-cool shades, skin tight vinyl pants, and passion for delivering George Michael tunes with more gusto than George himself could muster. Want that to go? The Sexy Sax Man combines Sergio’s smooth music with suave camera feature that inserts YouTube’s favorite sax man right into your photos. You can even use it to reserve a live “Saxogram” from the man himself. Candlelit nights will never be the same!

Napkin Sketch Stage ($1; pictured right): For seasoned music vets, the best medium for hashing out stage setups for a concert or tour is old, classic and never fails: the restaurant napkin. Decisions on where to put guitars, drums, pyrotechnics often arrive on the road, when the band is in a bar or diner, as Spinal Tap can attest. For a bit more than the price of several napkins, Napkin Sketch Stage updates this tried-and-true technique for the 21^st century with an iPhone app that packs the spontaneous freedom of humble tableware with point-and-tap features and the ability to save your brilliant stage decisions in secure locations. (No offense to your pocket, but a hard drive or email inbox is better.)

Google Android

Google Music Importer ($4): This app imports your Google Music library and playlists stored in Google’s music cloud to play locally on the player of your choice, while preserving song information and album art.

Volume Ace ($2): A global volume controller that works across all of your apps, Volume Ace lets you set volume based on time of day; program sound profiles that switch between your headphones and your home/car stereo; and a host of other volume customization options.

DJ Studio 3 (free): This free DJ app from the maker of Pocket DJ Vintage lets you track, scratch, pitch, EQ and loop music from your Android device’s library using virtual dual turntable interface. The app is technically free, but if you want to get past the one-minute playback limit, you’ll need to shell out a buck through in-app purchase. At least you can try before you buy.

PandIn – Pandora Plugin | GrooveIn – Grooveshark Plugin | SpotIn – Spotify Plugin (free): These apps can build playlists in the Pandora, Grooveshark, and Spotify Android apps, respectively, based on tags you make in other apps, without the need to close out of those other apps — pretty useful. It supports SoundHound, Hound, YouTube, Shazam, TuneIn Radio, musiXmatch, and Google Shopper. (We know, it’s a confusing feature set — you might want to check out the demonstration video for PandIn to learn more about this one.)

Web Apps

ListenToYouTube (free): Despite being originally designed as a video site, YouTube might be considered the most popular music service in the world. As its title suggests, ListenToYouTube lets you turn YouTube music into MP3s for your legally-questionable enjoyment later. It’s fairly straightforward: enter the URL of a YouTube clip, choose a sound quality option, click go, wait a few minutes and out pops an MP3. The high quality option sounds fantastic and clear (assuming the source audio was also high-quality). Even a clip of the Hellacopters’ drummer playing on a drum kit made out of ice sounded crisp. While we wouldn’t recommend pirating audio wholesale, this is a great app for collecting songs that will never end up being officially released, like that series of old Sesame Street pinball animations, stand-up comedy snippets, and so on.

New App Directory

The revamped Evolver.fm is also home to a shiny new directory of hand-picked music apps for nearly every platform — the first of its kind on the web — curated to make discovering and downloading new apps on just about every platform easier than ever.

There, you’ll find all the apps mentioned in this week’s installment as well as previous issues of This Week In Music Apps and Evolver.fm reviews with screenshots, feature descriptions, links to all of the app stores, and more.