This was fairly difficult to do and I am not a song specialist... So this document needs and wants careful proof-reading. The facsimile links are provided for each piece so it should not be too hard to do!

Milán lived in Valencia at the brilliant and cultivated court of the vicereine Germaine de Foix, which he described in a manual of courtly behaviour (1561). His most noted work is El Maestro (1536; “The Teacher”), a collection of vihuela pieces and solo songs with vihuela accompaniment. This was the first of a series of vihuela books that became one of Spain’s most distinguished contributions to 16th-century music. The pieces in Milán’s book are arranged in order of difficulty. The songs—Spanish and Portuguese villancicos and romances and Italian sonnets—are often of great beauty, and the instrumental writing is varied and resourceful. Milán is noted as the first composer to provide tempo indications in his music. (Encyclopædia Britannica)

There is a fairly large literature concerning those songs, a lot of it available on the WEB and the songs were recorded a number of times. The best of those in my opinion is that of  Jacob Heringman and Catherine King, where  Catherine King makes use of "diminutions" in the voice part.

One big question is why Milan decided that a singer could easily pick the notes from the vihuela tablature. He was not the only one in Spain at the time to indicate the melody using red tablature glyphs, but I tend to think most singers would find it impractical at best. One possible solution is that the singer was already expected to know the melody and that the tablature was coded to follow that basic frame. This makes somewhat more sense to me. But then the vihuelist was also expected to be the singer, so this point is moot...  Some of our modern assumptions perhaps get in the way, like the necessity and usefulness of separating voice and instrumental parts.  

Note: DjangoTab allows you display the tablature in notation mode still with highlighted melody notes in red.