Chris, that's a good question. This is not an exact rhyme, but what is called a "slant rhyme." Remember that the final "b" in lamb is silent. So that leaves is with frame and lam (but not lame. which would have made an exact rhyme but no sense). You could call it an imperfect rhyme, but 'slant" is better when you are certain that the poet knew that he was doing it, and had a good reason for doing it. In hymnody, if you want the end a line with Lamb (for emphasis) you don't have many exact rhyming options. So you may see in hymns words such as "calm" and "blame" used for slant rhymes with Lamb. I hope that helps!
How would the poet have pronounced “frame” and “lamb” so that they rhymed? Or is it just an imperfect rhyme?
Chris, that's a good question. This is not an exact rhyme, but what is called a "slant rhyme." Remember that the final "b" in lamb is silent. So that leaves is with frame and lam (but not lame. which would have made an exact rhyme but no sense). You could call it an imperfect rhyme, but 'slant" is better when you are certain that the poet knew that he was doing it, and had a good reason for doing it. In hymnody, if you want the end a line with Lamb (for emphasis) you don't have many exact rhyming options. So you may see in hymns words such as "calm" and "blame" used for slant rhymes with Lamb. I hope that helps!