Dear Agata Kubiak,

I thank you for your very important question as my new project devoted to this topic. You mentioned about "Interdisciplinary approaches very welcome". If I have understood this phrase correctly, then I want to share my thoufgts. Currently I'm developing a Singing Site (as a Song) where will sing the voices of famous singers Feodor Chaliapin, Enrico Caruso, Luciano Pavarotti, Placido Domingo and Dmitri Hvorostovsky. I will play the piano my improvisation accompanying their magic sounds. I hope it will be a new musical genre as a Interdisciplinary Approach "Mathematics + Programming + Music".

Hello Agata Kubiak! Maybe this article I can help you with (in Portuguese). See what you think and then tell me! Good reading! Thank you!

Edson.

Conference Paper O instrumento harmônico e o canto

Hi Agata,

I am basically from the Indian classical music tradition and a s such, vocal or instrumental performance is solo-oriented, thus each performer makes music and project her/his know-how with one discipline, either vocal or instrumental.  However, a vocalist more often than not plays the Tanpura or Swaramandal with a view to providing a drone or tonal accompaniment.  By the way, please read my article entitled, A Reflection on the Aesthetics of Indian Music, With Special Reference to

Hindustani Raga-Sangita on SAGE Open Publications.

Regards

Santosh

You may want to look into the Spanish Renaissance. The villancico settings for vihuela and voice sometimes display a vocal melody doubled in the vihuela accompaniment. Further back into history, the tradition of Greek lyre singing is likely a rich topic. It may be somewhat tangential, but in Jazz, "non-mouthpiece" instrumentalists sometimes hum or sort of scat along with their soloing . . . 

Hi, Agata Kubiak! There's a piece from italian composer Giacinto Scelsi, "Maknongan", that was played by Joëlle Léandre in the contrabass, and she used her voice in the recording, although Scelsi did not demand such voice. There's a recording on Youtube.

There's also Matthew Sharp, a cellist and baritone, but I don't know his work very well. There's an interview with him in classical-music.com ("Meet the singing cellist").

There is one genre in folk Iranian music in which a performer engage in several role at once. The performer called "Bakhshi" in local dialect and he enrolls as a music performer, singer, shaman, story teller, folk practitioner and several other roles. You may look at researches by Stephen Blum and Ameneh Yousefzadeh for knowing more about Bakhshis.

Good luck 

It's not exactly research, but definitely working checking out is Wendy Richman, who sings and plays the viola at the same time.  She recently recorded an album doing this;  vox/viola project:

https://music.illinois.edu/event/guest-artist-wendy-richman-voice-and-viola

http://steinhardt.nyu.edu/music/strings/faculty/richman

Fantastic! Thank you very much