Although primarily known as a composer, Issie is also an active baritone sax player, having performed at most of the UK's leading concert halls, festivals and jazz clubs, with various bands and ensembles including:

Royal Academy of Music Big Band 
National Youth Jazz Orchestra
Deptford Dance Orchestra 
Jools Holland's Rhythm and Blues Orchestra
London Jazz Orchestra
Theo Gordon's Funky Big Band
Grand Secret
Mambo 'til Monday (Own 10 piece latin band)
Ingredient F (Own 10 piece funk band... with 4 singers!)
Vortex Foundation Big Band, led by Annie Whitehead.

Issie's also played baritone in various collaborative projects with members of the Philharmonia Orchestra and Orchestra of the Age of Enlightenment (performing in venues such as Glyndebourne Opera House, London's Festival Hall and Purcell Room, Basingstoke's Anvil and Leicester's De Montfort Hall) as well as playing on some film and TV sound tracks (including sessions at Abbey Road!) and a number of other people's albums.

"Playing the baritone keeps me in touch with the reality of being a performing jazz musician, which in turn informs the way I compose. Jazz is such an interactive art form that I need to keep my feet on the ground and see what's happening in the here and now, so as to avoid being banished to that compositional ivory tower that sometimes leads to people writing music that's so far removed from reality, it just doesn't work. Better to keep my hand under the car bonnet and check out what's really making the jazz engine work, so I can draw on that enlightenment when developing the ideas that I have as a composer... and anyway, I love the sound and feel of the baritone. It's such a beautiful and expressive, as well as hard and funky instrument. Why would I ever want to stop?!"

More recently, as the sheer logistics of a touring international composer make it impossible for Issie to commit to playing regularly in other people's projects, the baritone has continued to be an integral part of her own projects, such as June 2007's collaborative quartet with Swiss composer and keyboardist Carl Rütti and fellow UK musicians Rowland Sutherland and Mick Foster.