Bob arranged Men of Harlech - and it's a cool arrangement.
I sing lead/co-lead on five of the songs. It's an attack laurel jamboree, or something. So yeah, I've pimped it now. Doing so has made me quite uncomfortable (I am in no way cut out to be a salesperson), so I will now babble on generally about music.
(Though now I've told y'all where to find it, I expect it will become a little more well known.)
There's a difference between people getting together to sing, and performing, I think - getting together, and the participatory nature of "bardic circles" (I'm afraid I rather hate the term, but feely admit that I don't have a great substitute) means that one can sing a single song for longer - as long as everyone is singing along with you. The death of a bardic circle is the person who insists on singing all thirty million verses of Greensleeves, solo, without any help or any instruments, and gets all snippy when you try to sing along. Even if they're not singing off-key (which they usually are), it's a sterile experience for the listener; they've worked out how the tune goes by verse two, and after that, if not allowed to participate on the chorus, they're just going to fidget and wish you'd stop. It's not really the reaction you want - and they're less likely to invite you if you insist on doing it every time.
In other words, don't sing twenty verses when four will do. A good rule of thumb for modern audiences (which is most people in the SCA) is to keep each piece not much longer than a rock song, especially if only one person is singing.
And no cheating and claiming Ina-Gadda-Da-Vida is the length of one song, and so you can sing for that amount of time. That fucker is 17 minutes long, and you know it. Most people in a Bardic circle will have fled long before you finish, and who wants to be the person that killed the evening's entertainment?
Honestly, most people don't have the attention span to sit through endless recitations of music they don't know. The more esoteric the music, the more careful you need to be - most people are somewhat unfamiliar with pre 19th century music. The rest of us live in perpetual fear of sitting through madrigal after madrigal - since that's all the period music most people know (including amateur singing groups, who insist on madrigals, even though there's oodles of great stuff out there that isn't a madrigal).
(I hate most madrigals - they're a sterile art form, like an etude. Some can be pretty, but basically, they're pieces written to excercise the voice and show off the tricks the composer can do. Give me a good meaty Tallis any day.)
(Om nom nom, Tallis. And a little Byrd on the side, if you please.)
(Ha, ha, a little musician's joke, there.)
But even your folk songs shouldn't be endless - unless everyone knows all the verses, and they're all happily singing along (everyone loves to sing in groups at bardics. It are a fact). Stick to three or four verses, and leave them wanting more, not wishing you'd shut up, already. If someone asks to learn your song, and is all starry-eyed about it, you're probably doing okay, but check your four-verse rule, just in case. They might just be sucking up.
The other problem with singing a fourty verse song is that your SCA audience will never tell you that your singing blows, even if you suck really, really bad. They'll sit politely, and applaud politely at the end, and reassure you that they liked it. Someone with completely cloth ears will always come up to you afterwards and tell you how great you were. I have seen this in action - someone gets up, drones an interminable song, and everyone applauds. Encouraged, the person jumps up again as soon as they can, and drones through another interminable song, and so on, until all the musicians have left, or someone "accidentally" trips and shoves the droner into the bonfire.
Lives can be saved if you find a good friend who will tell you the truth - sing to them, and ask for honest feedback. And listen - if they're scrunching up their face and saying "...it wasn't that bad", assume you suck, and either practice a lot, or restrict your singing to group singalongs. Try not to hear what you want to hear, and don't assume you're great no matter what your friends say (because they're just jealous and haters, and you're going to be a star someday, just like on American Idol) - you'll be a lot less likely to end up doing an "accidental" face plant into the fire pit. Yes, you may love the attention - we understand, really we do - but you'll get more positive attention longer if you keep it short and are willing to share the spotlight. People may even specially invite you to their bardics! Imagine!
Even if you're good, you have to remember that you are supposed to be entertaining. The audience is not your collection of paid minions, they're nice people who want to have a good time. Your job as a performer is to help them have that good time. Therefore, play to your audience, and even if you feel that your audience is a bunch of ignorant morons who wouldn't know period music if it screamed at them, please don't try to "educate" them with a three-hour epic version of The Pilgrim's Tale set to nose harp, or I'll come after you myself and teach you what "educate" really means.
And, on a personal note, stop singing the Moose song.