Dr Sandra Toledo-Rivera

Sandra began her musical journey at a young age, reaching a significant milestone at age 10 when she was accepted into the Youth Programme at the National Conservatory of Music in Mexico. Through this programme, she performed extensively with orchestras across Mexico City and participated in chamber music performances for esteemed organizations such as the Diego Rivera Museum, the Ex-Convent of Saint Theresa, and the Cuban Embassy in Mexico, among others.

In 2003, Sandra attended the Summer Strings Programme at the Regina Conservatory in Canada, where she participated in Master Classes with Jonathan Ward and Eduard Minevich. As part of the programme, she performed in recitals at Queen City Collegiate and Wascana Park Bandstand. That same year, at the age of 12, she was accepted into the Concert Violinist Bachelor Degree at the National Conservatory of Mexico, studying under Víctor Barrera-García. Her studies involved numerous performances with the conservatory's chamber and symphony orchestras, including a collaboration with the Mexico City Philharmonic Orchestra in 2006 and several solo recitals.

In 2009, Sandra served as guest Concertmaster for the Adolfo Ramos Chamber Orchestra and the Kejel Concert Camerata. She also received an artistic scholarship at Anáhuac University while pursuing a medical degree. She completed her Concert Violinist degree in 2010.

From 2010 onwards, Sandra balanced her medical studies with an active performing career. She secured a part-time position as a first violinist and soloist with the Tlalnepantla Philharmonic Orchestra and regularly performed with the Anáhuac University Orchestra in both ensemble and solo capacities, where she played from 2012 to 2016. In 2013, she joined the Texcoco Philharmonic Orchestra at the invitation of their Upper Strings Fixer Amnael Orozco-Díaz. Alongside these commitments, she engaged in outreach projects, freelance performances, and studio work, including recording music videos with GDN Records, performing live with Laura Pausini, and she holds movie credits as a section violinist for the feature film A la Mala by Pantelion Films.

After completing her medical degree in 2016, Sandra moved to the UK to pursue a Master's and later a PhD at the University of Sheffield. During her studies, she played first violin for the Sheffield University Symphony Orchestra and served as both first violin and soloist for the Sheffield University Chamber Orchestra until 2020. Since 2016, she has been a first violinist with the Sheffield Philharmonic Orchestra, where she also held the role of Upper Strings Representative from 2020 to 2024.

In 2018, Sandra founded the Weston String Quartet, and in 2020, she joined the first violin section of the Sheffield Symphony Orchestra, where she continues to perform. She has also collaborated frequently with the Sheffield Chamber Orchestra, Hallam Sinfonia, Sheffield Guild of Strings, and other ensembles in the city. In addition to performing, Sandra is an active violin teacher, with several of her students earning artistic scholarships across the UK.

Dr Amnael Orozco-Diaz

A Mexican violist and cellist, Amnael began his musical journey learning and playing the violin in the streets of Mexico City. A fateful accident in his teenage years nearly cost him the use of his left hand, but through resilience and dedication, he became one of the few professional string players to perform left-handed. His distinctive approach to string technique has shaped a unique career, marked by technical innovation and evidence-based teaching. He studied viola under Javier Montiel of the Latin American String Quartet at the Ollin Yoliztli conservatory in Mexico City, and has studied courses on Violin and Viola Teaching from Northwestern University (USA), and on Rehearsing Music Ensembles from University of North Carolina at Chapel Hill (USA).

His early career saw him play viola at university for the Tecnológico de Monterrey's String Quartet participating in public engagement events; as well as playing as an extra violin for the Philharmonic Orchestra of the Arts. He later served as Concertmaster for numerous outreach projects before securing positions as 3rd chair viola with the Mexiquense Symphony Orchestra, later with the Ollin Yoliztli Philharmonic Orchestra, and eventually as Co-principal viola with the Texcoco Philharmonic Orchestra. He also participated in music videos for GDN Records, played as a studio musician in diverse performances with international artists, and has movie credits (and a solid five seconds of screen time in the trailer) as Principal Viola in the production of feature film A la Mala by Pantelion Films in 2014.

Following the dissolution of the Texcoco Philharmonic in 2014, Amnael embarked on a transformative journey of self-discovery. During this period, he produced a significant body of arrangements and developed his unique approaches to viola, cello, and vertical viola techniques, which he continues to teach today. Fate brought him to the UK, where he returned to the concert stage as front desk of the Sheffield University Symphony Orchestra and the Sheffield University Chamber Orchestra up to 2020. he was also invited as Principal Viola for the 2016 Penine Spring Music Festival, and has regularly collaborated with the Music Department at The University of Sheffield as well most other ensembles in Sheffield.

Along with Dr Sandra Toledo-Rivera, he founded the Weston String Quartet in 2018, performing in recitals and for hire across South Yorkshire. As a regular engagement, he has been Principal Viola for the Sheffield Chamber Orchestra since 2017, and Principal Viola for the Sheffield Symphony Orchestra since 2020, with a performance of Cecil Forsyth's Viola concerto in March 2025 with the latter.

Amnael is also an accomplished arranger, with a growing catalogue of published works under Hal Leonard, primarily focusing on string quartet music and viola solo pieces. He teaches privately in Sheffield and recently joined the Sheffield Music Hub as a violin, viola, and cello instructor. His students have gone on to lead sections in the Sheffield Youth Orchestra, with others securing artistic scholarships to further their education beyond Sheffield.