I've been using two iApps recently for my music. These are for the iPad, and I don't know if there are Android versions available.
The first of these is ForScore. This is an app that allows you to download PDF music scores from the web or Dropbox (or upload from your computer via iTunes). The organization is excellent; scores can be grouped into set lists, sorted, and bookmarked. Turning the page is as simple as a quick tap to the right of the screen, or left to go backward. Images can be zoomed using standard gestures, and the app supports both landscape and portrait modes. In addition, there's a metronome function, and the ability to add your own notes to the page.
I'm using for virtually everything these days - as you can see over at the Fiddle Club website's "Community" section, there are a lot of old music scores now scanned and available in PDF format, and they work very well with this app, and it's easy to print to PDF with your own favorite music software, or scan a paper score to this format.
If I have a complaint, it's how some PDF images are rendered by some music programs - leading to an issue where on lower-resolution iPads, it's unclear if a note will be on a line or space until you zoom in. So far I've only run into this issue on shareware music printing software with an iPad 2 (mainly that issued for the City of Alexandria Pipes & Drums), and expect that with a more recent iPad, with a Retina display, the issue would go away.
The second app I've been using a lot is called The Craic. This app takes advantage of the text-based .abc format to store tunes. Not only can you import your own .abc collections from your hard drive, import .abc tunes from emails and your DropBox, but it also has a search function to scour the web for tunes in this format through various dedicated search engines. This means that you can find multiple versions of many traditional tunes within the app itself, if you need to quickly find something.
In addition, The Craic includes a playback function (using a flute voice), with variable tempo.
The app produces very attractive sheet music on your tablet's screen, but can also send music to printers via AirPrint, or via email. This puts it far ahead of my old favorite .abc program, a PPC Mac routine called Barfly (which, sadly, has not been updated for Intel Macs and the recent OS versions that no longer support CarbonLib, specifically 10.7 and above).
The Craic is in its earliest forms, and there are some issues with it still. First of all, it does not support all .abc's various extensions yet, like multi-voice - meaning your 4-part scores will not render in the current version. The playback can not use other instruments, and its tempo slider is far too small, meaning it's hard to get the tempo you want. Furthermore, the app does not recognize tempo headers in the tunes themselves; if it did, and used that as the center of the slider's range, one would be able to get more appropriate results out of the playback. Editing tunes is possible in-app, though the interface window is small, and it might be easier to do major editing and composing on a desktop, and then tweak and read with The Craic. Also, The Craic prints chords above the melody line, as Irish players are accustomed to seeing, and not below, which seems more common among Scottish musicians, and there appears to be no option to reverse the display.
I'll be still using Barfly to create my tunes, but the quality of printing in The Craic is so much better that it's likely that I'll be using it to store, display, and print my final scores from now on - at least the ones that use a single voice. I look forward to The Craic's continued development, and the addition of new features.
Next time, I'll talk about some tuner and metronome apps I use.