[4] Ionascu's musical career began shortly after graduating from Manchester in 1993, when he was appointed Vicar Choral at Wells Cathedral Choir, a professional singer performing on a number of broadcasts, recordings and international tours.

[5][6] On completion of his PGCE, Ionascu moved to Oxford, where he became Head of Academic Music at Radley College in 1997, launching his choral conducting career by founding (and conducting) The Laudate Choir, with whom he made a number of recordings over the next few years, performing with the English Chamber Orchestra and the City of London Sinfonia.

The following year, Ionascu undertook a six-month conducting fellowship in Australia, seconded to the Cathedral Choir of St. Andrew's school in Sydney, leading workshops and masterclasses across New South Wales.

[16][b] In 2012, he conducted the Crypt Choir with the English Chamber Orchestra to accompany the Tenor Mark Padmore at Canterbury Cathedral.

[21][22] In 2024, Ionascu relinquished his teaching position at Winchester and was appointed conductor and musical director at the Twickenham Choral Society.