In the Middle Ages popular devotion, encouraged first by the Servite and later by the Passionist orders, discerned and contemplated seven especially sorrowful moments in the life of the Virgin Mary: 1:) the prophecy of Simeon at Jesus' Presentation in the Temple, that a sword (understood figuratively) would pierce her heart in association with the opposition to Jesus; 2.) the flight of the Holy Family into Egypt to escape the murderous intent of King Herod; 3.) the incident in which Jesus was lost in Jerusalem at the age of 12; 4.) her meeting with Jesus as he carried his cross to Calvary; 5.) her standing beside the cross; 6.) her holding of his body when it was taken from the cross — the popular "Pietà" subject of sculpture and paintings; and 7.) the burial of Jesus.
For the Mass of the day, the sequence (a hymn to be sung between the epistle and gospel readings) Stabat Mater was composed. When I was a boy the hymn was sung to a fairly simple chant melody during the popular Lenten devotion called the Stations of the Cross — one stanza for each of the 14 stations. (Something similar happened with the sequence "Dies Iræ," which was originally written for the first Sunday of Advent, when the scripture readings referred to the final judgment at the end of the world. Bu it came to be used in Masses for the dead — Requiems — and as part of the Requiem it has received notable treatment by many composers, most spectacularly Berlioz, Verdi, and Mozart, IMO.) As wiki notes, the hymn has been given musical settings by numerous composers, famous and obscure. One of the most notable is that by Pergolesi in the early 1720's. (I think Abbado takes the tempo a bit on the slow side in the link, but you can find others, such as Scholl and Bonney, in the links to the video.) I'll put links to examples from other composers (and my Latin joke) in my music blog.
The name Dolores means "Sorrows," and is clearly a reference to Mary under the title Our Lady of Sorrows.
The prayer for the Mass of the day — which reads "Father, as your Son was raised on the cross, his mother Mary stood by him, sharing his sufferings. May your Church be united with Christ in his suffering and death and so come to share in his rising to new life, where he lives and reigns with you and the Holy Spirit, one God, for ever and ever." — might give us some pause if we think carefully about what we're asking for. But taking up our cross is no more than what Jesus says is required of all his disciples. We see Mary as leading us on the way, and we know that we all have our sufferings — it is just a question whether we choose to unite them with our following of the Lord so as to join Paul in filling up in our bodies what is lacking in the sufferings of Christ for the sake of his body, the church.
