[4] Diminuendo's dam, the American-bred mare Cacti, also produced Pricket, a filly who finished second in the 1996 Epsom Oaks.

[9] On her three-year-old debut, Diminuendo started 7/4 favourite for the Nell Gwyn Stakes, a trial race for the 1000 Guineas, over seven furlongs at Newmarket on 12 April.

In a change of tactics, Cauthen sent the filly into the lead from the start, but in the final quarter mile she was overtaken and beaten into third place by Ravinella and Dabaweyaa.

[11] Twelve days after her defeat at Newmarket, Diminuendo was moved up in distance for the Musidora Stakes over 10+1⁄2 furlongs at York.

Diminuendo was held up by Cauthen in the early stages before moving up to join the leaders in the straight but soon came under pressure and it was only in the final strides that she caught the Michael Stoute-trained Melodist to force a dead heat.

[15] Melodist, the winner of the Oaks d'Italia was also owned by Sheikh Mohammed, whose Kildangan Stud sponsored the race.

Ridden by Walter Swinburn (Cauthen was injured),[18] she was made odds-on favourite, but was beaten a length by the colt Minster Son.

[19] After reaching fourth place early in the straight she faded in the closing stages and finished tenth behind Tony Bin.