Donninelli in 2005 and subsequently studied at the Real Conservatorio Superior de Música in Madrid as well several Masterclass throughout Europe with important classical and modern soloists. The Italian has received awards at several national and international contests of musical execution and given more than 500 performances in Europe and the United States.

​Walter´s teaching experience includes several international courses and conferences: Corsi musicali estivi Eurydice (Levico, IT), Masterclass at Stanford University (S. Francisco, EE.UU), XVI World Saxophone Congress (Ljubljana, SLO), Masterclass Saxinsieme (Trieste, IT), I, II, III Masterclass cittá di Latisana (Latisana, IT), 3º Saxophone Festival (Pontebba, IT), Masterclass "Solisti di Confine" at Gradisca (Gorizia, IT).

In 2006 he recorded his first CD, TWO FANTASTICS, with the pianist R. Silvestre. The CD includes some of the most representative contemporary pieces for piano and sax, contaminated by popular cultures from different countries (T. Yoshimatsu, P. Iturralde, I. Gotkowsky, A. Corghi, J. Takacs) and received excellent reviews from composers and musicians around the world.

In 2007 he settled in Madrid where he currently lives with his family and created the Walter Sax Big Band, a stand-out jazz band in the Spain scene, and the WS Academy of music (www.waltersaxacademy.com). The school focuses on the study of the saxophone (at differetnt levels) and the creation of instrumental combos, significant meeting points for students and professionals. The goal of the Academy is to offer not only individual lessons to their students, but an opportunity to play in bands and give concerts, an essential part of their musical enrichment and crucial to nurture their enthusiasm.

Walter produced and published the CD INCOGNITO in february 2016, that contain own compositions for solo curved-soprano saxophone and new techiques of execution, and his last CD "Walter Geromet plays J.S. Bach" in juny 2017.