Tablet computers

Click picture to magnify 
Photograph of 
Storage Options Scroll Engage tablet computer connected to Fender Passport PD150+ amplifier
Scroll Engage connected
to Fender PD150+
Photograph of 
Samsung Galaxy Tab S2 8" tablet computer
Samsung Galaxy Tab S2 8"
tablet computer

With a large number of albums and tracks of folk dance music now available for purchase as ".mp3" files, a means of using these for folk dancing is required. The obvious choices of a smart mobile phone or a pocket-size MP3-player can be diffcult to use. The size and controls on such devices which have a touch-sensitive screen of limited size, tend to be very small. You need to be dexterous and careful to manipulate one of these devices while calling. Instead I use a tablet computer with an 8" touch-sensitive screen as a large-screen MP3-player.

The most widely known of such devices is the Apple iPad Mini. However, this tablet does not allow external storage to be inserted. This means when the device dies, which it will as the rechargable battery can not be easily replaced, then music and any other data is lost or at best has to be downloaded/installed again. Apple charges significantly more for versions of this device that have increased internal storage. Devices from several other manufacturers have a slot to insert a micro-SDHC card. This means the whole collection of music, images, and so on can be removed for transfer to or from another device, including a PC.

I have used two such tablet computers. Both run under the Android operating system which is produced by Google and is based on the Linux operating system.

  1. The Scroll Engage 8" tablet was manufactured by Storage Options.

    The picture on the above right shows this on an Arkon folding tablet stand (an excellent piece of kit) with the tablet's headphone output connected to the stereo input sockets of the Fender Passport PD150+ amplifier.

    This tablet runs Version 4.0 of the Android operating system; this version is also known as Ice Cream Sandwich or ICS.

  2. The Samsung Galaxy Tab S2 8" is a more powerful device. It is more responsive and starts-up much more quickly. Both attributes are useful when calling folk dances to recorded music.

    The picture on the right shows it with a stereo cable for connection to amplifier (or headphones) and a miniature USB connector which also provides power.

    This tablet now runs Version 7.0 of Android which is known as Nougat.

When preparing either of these Android tablets, they can be connected to a PC via a USB2 cable. For a PC running MS Windows, the internal storage on the tablet and any micro-SDHC card that is plugged into it, appear as drive(s) to, and from, which files can be transferred. If you want to delve deeper into the innards of the tablet's operation, then debugging modes and software allow such access from a PC over the USB link.

Android music player app - PowerAMP

Screen shot of PowerAMP app 
playing track 'Miss Sayer's Allemande' from album 'Kenton Ramblers 1978'
PowerAMP app with screen
in portrait orientation

Although Android installs a default music player application (or "app"), a range of other music player apps are available. Finding one with suitable behaviour and features to use when calling folk dances turned out to be rather less straight forward than I imagined.

All the players that I've tried have on the screen:

|| a "pause" button, and
<< a "go back" button.

However, none of them (in their supplied Android version) have a "stop" button to move back to the beginning of the track that is currently playing and wait.

The problem with the "pause" button is whether or not the paused state persists when you perform other actions, such as going back to the start of the track that is currently playing or moving on to the start of the next track of music. When calling it is much, much easier if a pause persists.

The "go back" button can do one of two things when it is pressed in the middle of a track (whether actually playing or paused): it can go back to the start of the current track or to the start of the preceeding track. The latter behaviour is a real nuisance when calling.

I settled on using PowerAMP because, amongst many useful features, it has the following characteristics:

  1. Persistent pause. When || is pressed followed by << or >> it does not start playing immeadiately. For calling dances this is the behaviour that is required.
  2. There is an option to decide how the << behaves. Unfortunately the default is to go to the start of the previous track so this setting has to be altered; it only needs to be done once.
    ≡ → Settings → Look and Feel → Player UI → Button Resets Current Track
    Make sure this option is on.
    Note that even with this option active, pressing << when the play point is at, or very close to, the start of a track moves back to the start of the previous track in the album or playlist. This is acceptable, indeed very useful, behaviour.
  3. PowerAMP builds and maintains its own database of music files (such as ".mp3"), the directories (that is folders) where they are stored, the track titles (which are inside each ".mp3" file) and the album to which they belong (also within each ".mp3" file). You can define which areas of storage should be scanned to find music files. Usually the scanning occurs automatically when changes in these areas are detected, but a scan can be requested. PowerAMP goes even further, as a complete rebuild of the database can be forced. Having suffered the consequences of another music player (not PowerAMP) corrupting a database, but offering no means to rebuild it, this capabiltiy in PowerAMP is very reassuring even though I have never had to use it.
    It should be noted that PowerAMP does not use the music database that is set up and maintained by the default Android music player and the operating system. Again this is reassuring as the default Android music player and its database remain as an independent fall-back.
  4. PowerAMP can export and import playlists as ".m3u8" files. These are simple text files which list the directory and filename of the music tracks that form the playlist. Being text files, they can be manipulated or generated by any software that can edit or write a text file. Such software can be on the tablet or on other computers (such as a Windows or Linux PC).
  5. Album art is well displayed at a large scale, optionally with a co-ordinated background.
  6. Although I normally use an 8" tablet in portrait orientation (see picture above), PowerAMP also works with the tablet in landscape orientation. However, in recent versions the time indicator line displayed when in landscape mode has become too short to be of much use when glanced at while calling.
  7. When navigating to locate a track to play, among the options for grouping tracks are:
  8. At Version 3, Poweramp has, at long last, introduced a facility to change the rythm, that is the tempo, of music (without altering the pitch), and it is controllable in 1% steps of speed. An extremely useful capability when playing music for folk dances.
  9. PowerAMP is not free software, but the current price (Oct 2021) of £4.50 (GBP) is, in my opinion, good value for money.

Of course, no software is ever perfect for a particular application (unless, that is, you have written it yourself). Four problems with PowerAMP are:

Photograph of Graham Foster's dance cards and boxes
5″×3″ dance cards

I keep information about dances on 5"×3" cards, with detailed instructions on the front and calling prompts on the back (see picture on right). The risk of loosing these (an evening's programme, or worse a whole boxful) worried me for many years. Access to digital scanning provided a backup, and a tablet computer takes this further as it means images for all my hundreds of dance cards can be immediately available. I still use the cardboard versions as reminders when calling an evening's programme, but it is useful having the full set of images easily to hand to satisfy requests and queries.

Screen shot from Android tablet
Screen shot of Simple Gallery Pro showing
front of a dance card

Screen shot from Android tablet
Screen shot of Simple Gallery Pro showing
back of a dance card
I scanned and stored the images as 750×450 pixel ".png" files, and each dance takes about 1 MB (around 600KB for the front, 400KB for the back). The Portable Network Graphics (".png") format for images uses a lossless compression algorithm. The storage space required for each card could be considerably reduced by: using image editing software to remove the faint blue & red rulings, reducing the number of colours, and using ".jpeg" lossy compression. However, the original intention was for archive/back-up purposes and the sum total for all my dance cards without these techniques is under 1GB and so is insignificant on a 32GB micro-SDHC storage card.

The Gallery app for viewing images that is supplied with Andoid has poor navigation facilities, although recent versions do allow the ordering of images by file name; earlier versions insisted on ordering images by date which was utterly useless!.

Fortunately there are numerous alternative apps. Simple Gallery Pro from Simple Mobile Tools is an appropriate app and, at the time of writing, was free. The two screen shots on the left show the appearance of Simple Gallery Pro when it is displaying each side of one of my cards. You can move between these two images by swiping a finger across the screen. The annotation and the control buttons that are visible in the upper shot disappear (or re-appear) when you tap the screen. The lower shot shows the uncluttered appearance without them.

It should be noted that recent versions of the QuickPic app, which I employed and recommended in the past, are now plagued by full-screen pop-up adverts that make it just about unusable.

Unfortunately I have yet to find an Android app that can read a "playlist" of images. All apps for displaying images, including Simple Gallery Pro and QuickPic, will display or move-through the images that have been placed together in a folder (i.e. a directory), but this means copying the images that constitute a programme of dances into such a directory, a process that would be unecessarily wasteful of storage space. For such an app the images would also have to be renamed or re-dated to ensure they come up in the required order. I have, therefore, implemented a web application (running within a browser) that reads an ordered list of image file names and displays each image. When used with a touch-sensitive screen, movement between the images of dance cards can be done by swiping. Please contact me if you would like further information.