Using the Buntús Cainte MP3 Course on a Nokia smartphone (e.g. Nokia 5800 or Nokia N97)
As Michelle mentioned above, the built-in MP3 player on Nokia smartphone can't display the lyrics embedded in MP3 files. This means that you won't be able to read the Irish and English translations while listening to the audio course.
Fortunately, there is a third-party MP3 player you can install on your phone that will let you do that. It's called LCG Jukebox and you can get it here: http://www.lonelycatgames.com/?app=lcgjukebox (use the Symbian download link on the left-hand side to download the trial version).
I've tried it on my Nokia 5800 and it works fine. Once a Buntús Cainte lesson is playing, tap the small pen icon to display the Irish and English translation. The pen icon is really tiny so you might need to use the stylus to get to it but once the lyrics are displayed, you can scroll easily with your finger. Here are a couple of screenshots:
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It's not the prettiest application ever but it does the job. Note that it's not free - it costs $19.50. There's a free trial however.
LCG also have an Android and a Windows Mobile version of this MP3 player. So if you have an Android or Windows Mobile smartphone, you could give it a try to get Buntús Cainte working on your phone.