There is a song simply called "April" from "Arky's Toast" LP From the Half Moon to the Rising Sun, Greenwich Village GVR 212, 1979.

It is also on the CD "Maypoles to Mistletoe" Leader, LERCD2092.

It's also sung by "Jolly Jack" as "April Song" (CD "Seasons, Cermonies & Rituals" Fellside, FTSR 5

Also:
20th of April, Oysterband
April 1918, Steve Byrne
April Friend, Nancy Kerr & James Fagan
April Morning ('twas on one April Morning, Young Men are false): Folly Bridge, June Tabor, Wilsons, Lou Killen, Norma Waterson, Tony Rose, Cyril Tawney, Pilgrim's Way
The April Fool Tape: Nicols/Swarbrick (Cropredy Box)
When April came to Rhymney:

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APRIL FRIEND James Fagan · Nancy Kerr · Colin Fletcher    https://www.youtube.com/watch?v=U6g-4wandPU
WHEN APRIL CAME TO RHYMNEY - Poem by Idris Davies set to music by Gerhard Obwegeser    https://www.youtube.com/watch?v=HRz_PiQhAoU